I don't know. I do feel like there's a scenario in which freeing up domestic gates at yyz, yow, and yul, AS WELL as aircraft to be used for other routes would be profitable for air Canada. Especially if they get to share in some of the passenger rail revenue.
I'd guess it would boil down to ac's casm (cost per available seat mile) and rasm (revenue per available seat mile) in the tor-ott-mtl triangle. If they are incurring large costs and lower revenues than other potential routes simply to squeeze out competitors and/or offer the convenience of near hourly departures, than maybe the math might work . Personally I don't know if the triangle is a profit center that is subsidizing other poor performing routes or if it is being subsidized by other routes (like say international).