Only problem is that the theory doesn't hold water. Air Canada has a limited number of aircraft. After that LGA->YUL flight, that same aircraft will then be scheduled on YUL->YYZ, then from there to who knows where.

So, as you say, they are a business. By calling a cancellation due to mechanical failures, the airline is then responsible for hotels and/or making alternate arrangements for the pax and they have to locate a replacement aircraft to fill in the hole left by the stranded aircraft. Furthermore, they will eventually have to ferry that aircraft out of LGA in order to rejoin the fleet, undoubtedly flying it without pax, costing them almost the same as flying it with some pax, but obtaining zero revenue.

If they see that a given route has low load factors, the only thing they will do is reduce the frequency of the route and/or downsize the equipment used on that flight. End of story.