Can't answer your question definitively, since the only guide I have is the Cdn+ GOLD one which specifies eligible fares on being: Y, B, H, K and M. On Cdn, M and B are the opposite of what they are on AC: M is the lowest eligible discounted fare for elite upgrading (Q, N, V and L are ineligible for upgrading with this year's stickers as they are on AC) while B is a slightly discounted economy fare, almost as flexible as Y, and like M is on AC. Hope this helps, but I'm sure when the sun rises over Calgary and Vancouver in a few hours, BB or AC*SE can give you a more definite answer.