The only 2 that I know of in Montreal are at the Palais de Congrès (convention centre). One is large and connects the main exposition halls with the conference centre, the other is much smaller. They're also connected underground.
Instead, there are over 30 km's of underground city or RÉSO (-15's?) which are interconnected with about a dozen metro stations. Every major office complex, shopping centre, 5 universities, 3 train stations, bus terminals, Place des Arts, Bell centre, Olympic Stadium, National library etc. are plugged into the underground. I've been exploring down there for over 2 years and I still get lost and I still haven't seen half of it.
Photos by me
The big one
The little one
RÉSO map