In two provincial referenda called by parti Quebecois provincial governments in 1980 and in 1995 to decide whether the government should be given the authority to negotiate separation (and a new association) with English-speaking Canada, the NDP called for a No vote, the CP and Maoists essentially called for a plague on both houses, and the Trotskyists supported the Yes side.
The problem for the left in Canada and elsewhere is that it has often found itself caught between its principled opposition to national divisions within the working class of an existing state, and the consideration that the most progressive sectors of the restless national minority - notably the workers and intellectuals - are often in favour of independence.
In Quebec, a majority of the French-speaking population favoured sovereignty, and the referenda failed narrowly only because of the monolithic voting behaviour of the historically more privileged English-speaking provincial minority, joined by recent immigrants with more of an allegiance to Canada than to the province. The independence movement has declined in the wake of the boom in the world economy since '95 and the corresponding desire of cosmopolitan young Quebecois to participate in it, but I think the movement could well revive if there is a global downturn.