I've never left from Montreal, but if it's anything like New York, or FLL, it's just a quick run to the port as they have to get back to the airport to pick up other passengers.
Now I may be wrong, but as no one has answered you, I thought I would try. I am sure you will see some of Montreal but not that much. There is so much to see in this lovely old city that you really have to spend a couple of days there, which we used to do when we had family living there.
Can anyone who has done the canada/new england cruise tell me if the transfer from the airport to the HAL ship is just a quick bus ride or do they give you a little tour of Montreal?
I've never done this run either, but I can't imagine they would throw in a whole tour ... not unless something were wrong and the ship were not ready yet for embarking. Usually it's just a run ... from the airport to the pier ... exactly what you pay for.