Just flew YUL > LGA on AA yesterday 3:30pm. With caveats that it was the day after the Grande-Prix, and that I came from landside, my observations;
Pre-Check was a significantly longer wait than normal security. 25 min vs 10 min.
TSA for US passport holders took maybe 2 min. Picture taken, waved through. Global entry looked to be about the same.
They preferred that we didn't use MPC.
Another 5 - 10 walk to gate. Long waits for food and restrooms, but...race cars.

57 min is too tight for my tastes, but if both flights are on Air Canada, you're protected.