As a habs fan and former Montrealer living in the GTA, as a kid/teen I always got really excited when the Habs would beat the Leafs, but then all my leafs fan friends would brush off the rivalry and go on about how 'they don't hate Montreal' and 'I cheer for the Habs when the leafs are out' yada yada...Even when the Leafs beat montreal, it was like any other game. 0 intensity toward it.
I always thought they were just saying that to avoid any more ribbing or cover their butts in case they did lose, but as I am getting older after having lived here for 10 years, the more I am starting to believe that is really their attitude. The habs are just a non-factor anymore. I think even if they two teams met in the playoffs and the leafs lost, fans wouldn't be upset per se, they would be angry the leafs lost but not because it was to Montreal. most of my Torontonian friends have nothing but great things to say about the city of Montreal.
This could be just the crew I hang with, but I find a lot of leafs fans tend to have more of a hate for the New York's, Chicago's, Pittsburgh's...essentially any major US metrolpolis. I think a lot of that has to do with the other Toronto teams(Raptors/Jays/TFC) and some rivalries with cities carrying over. There is no Winnipeg in MLB, or Calgary NBA team.
In conclusion, I think all other canadian teams fans hate the leafs but it's just not the same the other way around.