There is no legal obligation for the Prime Minister—at least, no legally defined obligation set out in the legislation, as currently worded. It is obvious—and I understand this—that for constitutional reasons, no such obligation is identified in the legislation, but I think one can expect that, if a consultation is held province-wide, it would probably be quite difficult for the Prime Minister or Governor General—as this remains the prerogative of the Governor General—to ignore the choice made by voters.
On April 9th, 2008. See this statement in context.