A clear referendum result would oblige the rest of Canada to negotiate Alberta's exit.
Claimed by: Commonly stated by Alberta independence advocates
Needs context: Accurate as written, but a key piece of context changes how it reads. How we rate.
Short answer
On this narrow point the advocates are right. The Supreme Court's 1998 Secession Reference held that a clear majority on a clear question would create a constitutional duty on the federal government and the other provinces to enter negotiations, a duty the Court described as reciprocal and binding in principle. The important caveats are that this is only a duty to negotiate in good faith, not a guarantee of independence, that the question and majority must be clear, and that any actual exit still needs a constitutional amendment. With those qualifications, the duty to negotiate itself is well established.
What remains uncertain
The claim can be accurate as stated, but important context changes how most people would understand it. The summary above supplies that missing context.
What the evidence shows
The Court held that a clear majority on a clear question would confer legitimacy on a secession initiative and impose a reciprocal duty on all parties to negotiate, while stressing negotiations might not succeed.
Supreme Court of Canada, Reference re Secession of Quebec (1998)
The Clarity Act enacts this, directing the House of Commons to determine whether a referendum question and majority are clear before any negotiations on secession may begin.