How well this happens in reality probably has to do with how well-established the concept of coalition is in that country's national political scene. Some countries are always governed by coalition and some resist the concept to an almost painful degree. In the English-speaking world only Ireland really has any tradition of coalition (the word is used in a different, and I would argue incompatible, way in Australia), and the UK's current experiment with coalition has so far not been a success at all (I measure this by the reaction to the Liberal Democrat Party by the public and especially by the people who voted for it).
Canada is at the other extreme. We talk a lot about coalition, but Manitoba is the only part of the country with any real tradition of coalition, and that was a long time ago. Our parties tend not to play well with others, even the Liberals and the NDP, the two parties most frequently mentioned in connection with the word 'coalition'.
Provincially, if the numbers merited it, could we develop a trdition of coalition? I don't know...
- Newfoundland and Labrador, Prince Edward Island and (most of the time) New Brunswick are pretty bipartisan - which ought to mean no need for coalition. Given that in each of these provinces the NDP struggles even to be taken seriously, they might appreciate being asked to be a junior partner, but it's seems unlikely they would be asked.
- Nova Scotia is legitimately tripartisan, and thus an obvious contender for coalition one day. Observing the Atlantic provinces as a whole, you see PC parties that are to the left of the norm and NDP parties that are to the right of the norm: it's a crowd at the centre, and you wonder why Maritimers even vote. But it tends to be about 'supporting a team', a group of individuals you find competent or trustworthy, as much as supporting their (overlapping) policies. There ought to be room for any kind of coalition in Nova Scotia - Lib/NDP (or vice versa) or Lib/PC (or vice versa) or theoretically even PC/NDP (or vice versa). I think given time Nova Scotians could warm up to it, but at the moment, it probably wouldn't go down well.
- If Québec continues to revolve around a PQ-PLQ axis, the ADQ would seem to be perfectly poised as 'perpetual junior partners', able to lie comfortably in bed with federalists and separatists alike, pulling the flexible politics of the two main parties in a rightward direction when the numbers warrant it. I think there is a place for a 'perpetual junior partner' party, and I think the ADQ could hold onto its vote percentages doing so. I could envision no curcumstance where the PQ and the PLQ could work together, and that leaves Québec Solidaire. I think QS would have a problem were Québécois politics to turn to coalition: their obvious dance partner would be the PQ, and it would be quite difficult to see them working with the Liberals or with the ADQ. But a PQ/QS coalition would, I think, marginalise QS. Their policies, both socioeconomically and constitutionally, overlap the PQ to such an extent that I don't know why someone pleased with a PQ/QS government would vote QS and not PQ. I hate calling a party a 'perpetual opposition party', but QS (love it though I do) kind of seems like that.
- Ontario has experimented with minority rule before, and has dipped its toes in coalition before running away shivering. Historically the Ontario PCs have been 'red' enough that a PC/NDP coalition would not have been crazy. But it's pretty crazy now, and Ontario realistically only looks like the federal scene seems to: some kind of Lib/NDP coalition (less likely, or vice versa) might happen (even at that it's doubtful), but the PCs would remain wallflowers.
- Manitoba looks closest to the UK right now (by which I mean the actual UK spectrum, not the apparent UK spectrum that convinced millions of leftists to vote for a centrist party this time out). A major party on the left and a major party on the right with a minor party in the centre is the perfect scenario for coalition: there couldn't be a PC/NDP coalition, but the Liberals could go to bed with either one. The numbers haven't required it for a long time now, but if they did, why not?
- Saskatchewan's a strange place. It likes its right-wing well to the right and it likes its left-wing well to the left. That ought to leave plenty of room for a centre, but the transformation of the PC Party into the Saskatchewan Party took a lot of Liberals with them, to the degree that the Liberals are very much a minor party in a very bipartisan system. I'm looking at the Wikipedia page of the Liberal Party of Saskatchewan, and it claims that the party views itself as a party of "Personal Liberty, Free Enterprise, and Responsible Government". With the Saskatchewan Party quashing foreign takeovers of the province's natural resources, we might be looking at a spectrum shift here. Either way, the only use the current Liberals would be is to prop uf the SaskParty (and with Wall's current numbers, that's not necessary). NDP/Lib looks pretty unlikely here.
- Alberta's just all over the map now. Famous as North America's most monopartisan district, it looks like Alberta might be undergoing one of its generational 'kick out one right-wing party and replace it with another' activities. With the numbers as they currently stand, you could surmise some kind of cooperation between the PCs and the Wilrose Alliance as possible, but where the politics overlap, the cultures don't, and a WRA vote is a vote against the PCs. There's no chance they could work together. What about the Liberals and the NDP? Well, I could see the Liberals propping up the PCs, but even that's not very likely. Alberta's politics have yet to stabilise, so there's no point surmising until then.
- BC's all over the map, too, but I don't really see the landscape changing that much long-term. If the BC Conservatives can establish themselves as a real presence, it would probably only be as a likely partner to the Liberals. Actually, if the Greens were able to establish electoral success, BC's political landscape could come to resemble Germany's, where a major right-wing party has a minor dance partner where necessary and a major left-wing party has a dance partner only when necessary. It works well in Germany, so we could find the historically dysfunctional BC electoral landscape suddenly transformed into a model for the rest of the country.
- Nationally... ah, Ottawa. More than any single province, Ottawa seems like spoilt children unable to share a sandbox. It is true at present that Liberal/NDP is the only real coalition that seems so much as conceivable, and even that might prove devastating for both. A sandbox where potentially both the Conservatives and the Bloc could be invited to play if need be is ultimately what we need. But that seems about as likely as Elizabeth May heading up a landslide-majority government.