Hemisph-Air is still around. They moved not too long ago; and yes you'll pay more for the privilege of flying out of YUL. It is accessible via PT (I know the route well!)
http://www.hemisphair.com/eng/
The St-Hubert schools are also accessible via public transport, although more limited. If I remember correctly, the buses stop running after evening rush hour. Find a friend with a car if you plan on doing any night flying!
Cheers!