I just noticed that a couple of stadiums (Montreal and Edmonton off the top of my head) have endzones that have their top corners cut off a bit; doesnt that go against the regulations of a cfl endzone?
I don't have the section number off the top of my head, but I do remember when reading the 2009 CFL rulebook that such is allowed.
The link to the 2010 version is available right via the homepage I think, and I believe the section about dimensions of the field is towards the beginning of it.
The field of play has to be a certain distance (I think it's five yards) from all obstructions which could pose a hazard to the players. If there is something like a wall that is too close to the playing field, the dimensions of the field can be modified. This means that the end zones can be slightly smaller, or even oddly-shaped.
I remember when the end zones were 25-yards deep, the corners were clipped at Ivor Wynne stadium; but now that they're just 20 yards, that's no longer necessary.