YUL only seems to require you show your BP to the greeter and then the stuffer (and a 3rd time if the peeper snags you and your laptop).

I've noticed that at some US airports when they board a Canadian bound flight, the GA makes a point of announcing that photo ID is NOT required during the boarding process, this is usually followed by half the PAX trying to stuff thier passports back into their carry-ons. This is an easy way of figuring out who on the place is returning back home to Canada and who is American or a FF