CP definitely used to offer a free round trip ticket to anywhere in North America to anyone who volunteered to be bumped from any domestic flight. This is obviously worth more than the $300 Air Canada now offers. I have no idea what Air Canada's policy used to be.
<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by Secret Agent:
We will also offer a guaranteed upgrade to those who volunteer, to sweeten the deal, based on availability on the next flight.</font>
I volunteered to be bumped last spring, and politely asked if I could be upgraded on the later flight as a result. I was refused outright and given a lecture about asking for upgrades on non-elligible fares. There was plenty of room.
I do feel that AC abuses their market position when flights are oversold. I don't think they should enter into a bidding war, but they should make more of an effort to get volunteers and perhaps offer slightly more compensation. It's a good deal for AC if they overbook by selling an extra full fare seat and only have to pay some leisure traveller $300 for his inconvenience.
Fortunately, it is very rare that people are involuntarily bumped. I've witnessed it only once in the last five years.