About YYZ--note that the regional jet terminal does not have the kind of "jetways" that most people on this thread are referring to. Toronto has small covered areas extended from the mini-terminal (which look like large tool sheds) which allow passengers to board unencumbered by snow and rain. The aircraft pulls into the gate area, the connecting sleeve comes over to cover the aircraft, and the CRJ door opens down into the covered area. This is quite different from the mini-jetways used by American Eagle, America West Express and others, which are literally miniature versions of the jetways regular aircraft use--allowing the passenger to not only be covered, but board the plane in comfort. In Toronto, when you're trying to board or exit a CRJ in the dead of winter in below-zero snowy weather like I have done, you know that it's a different kind of jetway entirely.
One more note about DCA-YYZ on AC's CRJ...when boarding, AC uses the gate next to the McDonald's in the second pier of Terminal B/C and has a set of airstairs rolled up to them, for boarding in all weather. Strangely enough, in about 10 flights total, I've never had a bad day weatherwise on departure, so I don't know what they do when it rains or snows. On arrival, though, passengers enter the terminal at ground level and walk up a set of stairs to an auxiallary door for the gate (the "A" gate).