The Atlantic provinces would have remained part of Canada.

Note that the "Maritime provinces" conventionally only includes New Brunswick, Prince Edward Island, and Nova Scotia. The Atlantic Provinces are the Maritime provinces + Newfoundland which only joined Canada in 1949.

When a country is separated like this it forms an exclave. Examples include Kaliningrad Oblast (which is a bit of Russia between Poland and Lithuania) and more familiarly, Alaska.

Another recent case: Bangladesh was formerly part of the country of Pakistan despite being on the other side of India from 1947-1971. To be fair that ended with a genocide and a revolutionary war, so probably not the best example.

It's possible that with Atlantic Canada disconnected the scene would be set for the country to split further in the future.

It is also possible that despite the secession of most of Quebec Canada would remain connected.

The political position of the federal government was clarified around 2000 when the "Clarity Act" was passed. This legislation says that in the case of a clear referendum majority vote in favor of secession in response to a suitably worded question that the provinces and federal government would enter into negotiation with Quebec for secession. It was passed after the Supreme Court of Canada answered questions posed in '98 by saying that the province of Quebec did not have the power to unilaterally separate.

• "Negotiations" here means two things. 1) Quebec does not have the right to unliaterally separate, although the government of Canada has an obligation to enter into negotiations to allow them to do so. 2) Negotiations here are taken to include the possibility of the Quebec being partitioned - much like Northern Ireland remained part of the UK when the Republic of Ireland seceded, the thought is that pieces of Quebec which would prefer to be part of Canada might remain so. The potential would exist then for some of the Quebec Atlantic corridor to remain - this page has some maps involving the partition of Quebec. This idea that Quebec could be cut up is considered outrageous by some separatists and is a bit controversial to this day.

• Re: the suitably worded question, Much has been much said regarding the way that the referendum questions have been posed. For instance the '95 referendum question was

"Do you agree that Quebec should become sovereign after having made a formal offer to Canada for a new economic and political partnership within the scope of the bill respecting the future of Quebec and of the agreement signed on June 12, 1995?

Federalist objections to this included the fact the question didn't include the word "country" that no framework for a "partnership" with the rest of Canada had been made, and that the question suggested that a "yes" vote was a ratification of something already decided, rather than regarding a decision to separate.

• "Clear majority" Suggests that the standard the government of Canada desires for a successful yes result might be higher than 50%+1. What a clear majority is is not defined.

While the '95 referendum was before this, it gives you an idea of how the government of Canada may have responded at the time.

On the other side, also in 2000, the Parti Quebecois (the separatist party in Quebec) passed Bill 99. It suggests that

• The people of Quebec have the power to unilaterally determine their political regime (i.e. negotiation with the federal government, or having the approval of any referendum question would not be necessary)

• a referendum standard of 50%+1 is sufficient to decide the fate of the province

• If Quebec secedes, international law would protect its territorial integrity.

These two opinions on how secession would occur are clearly incompatible. Open questions remain about what the legal status of both the Clarity Act and Bill 99 are under Canadian an International law. What exactly would take place after a positive referendum, or would have happened after a successful referendum in '95 is not entirely clear.