In economy it is not actually standby, it is same day confirmed and it is $50 and is based on Y availability and the flight not being oversold, if you're not an SE this is a better deal than $55 change fee as it is not restricted to Aeroplan availability. For business class you can stand-by for an earlier flight.
That was my understanding, but as I thought I made clear above, the new fees for award tickets are $50 to standby (in both business and econo) and $55 for a confirmed change (again, in both business and econo.)
Several different phone agents gave me the same story, as did two check-in agents. And in slightly surprising fashion, all five explanations were identical.
In my situation, I'm booked on and flying AC33 on the 77L. The 5pm, 6pm and 7pm flights are all wide open, and yesterday showed XM'd planes. However today the 5pm and 6pm flights are now showing 2-2-2 for the seat map, and while the 7pm is showing 1-1-1 (or 1-2, depending upon who you ask) it's showing as a 767.
I'm not about to pay for the 'privilege' of risking a 2-2-2 seat configuration to leave 90 minutes earlier. So I'll just load up here in the lounge.
At AC expense.