The most complex scenarios are also the most unlikely, and not worth dwelling on except to marinade in false reassurances. The most likely scenario is the single most dissatisfied province deciding to run itself. Since a negotiated exit is so complex, the easiest path - clean break, new constitution, drop all of Canada's obligations into Canada's lap, all immediately unnecessary baggage and entitlements cast aside, etc - is the most likely one taken.
The most likely scenario is also the most dangerous. A single separated province, consolidating federal and provincial governments into one, not needing to pay for many of the things a larger country wants in order to have seats at the international big boys' tables, is more likely to also be able to pay its own way. It is possible for two things to be true at the same time: lower GDP due to the frictions and losses of separation, but lower government expenses as a share of its GDP, thus lower tax burdens. Its fiscal position becomes envious; it is attractive to high-productivity immigrants; it prospers. If it doesn't need deficit financing, it won't care what the bond rating agencies say. If it doesn't care about what the bond rating agencies say, there is no reason to negotiate holding some share of Canada's fiscal obligations. Thus begins a game of musical chairs to see which fragment of Canada is left holding all of Canada's obligations.
If a basket-case province secedes, it will likely remain a basket-case. If a prosperous province secedes, it will likely succeed.
