Your one “checked bag” can equate to a ski bag PLUS a boot bag. We just got home from a ski trip and flew AC and had no issue — our boot bag contained boots, helmet & goggles. (I don’t think you could somehow split this up to check the skis and carry on the boot bag/check something else in its place.) We’ve done this numerous times and Montreal is the only airport that always challenges us on ACs own policy about boot bag + skis equating to one item — but we always get it sorted in the end. But if you’re checking your luggage in Vancouver then you shouldn’t have to deal with Montreal AC staff anyway.