Since the question was asked how liberal - with a small "l" - Toronto is relative to cities in America and Montreal in particular, I would say Toronto is among the most liberal around. I don't know enough about Montreal to speak, but at least Toronto is in good company with such a grand city to its east.
San Francisco is the bastion of liberalism in America for our larger cities. Both New York and Chicago have a large number of Democrats and Chicago still has an active Democratic machine, but that's just the political leaders. The people are more conservative than many other larger cities around the world.
Toronto is comfortably more liberal than San Francisco in a policy sense. San Franciscans live in a far more conservative country that has a stronger federal government. Because of this, the city's liberal leanings tend to get hit back by the larger system. San Franciscans can't enjoy true universal health coverage even though they are trying it on a local level just in the city boundaries, for example.
Toronto is where the viability of liberal leadership can be practiced in a real sense, hence why its both culturally liberal and can deliver those liberal politics through policy as opposed to dreaming about it as they do in San Francisco.
New York? As great and grand as the city is, it has a strong conservative community with many conservative institutions. Many so-called New York liberals are actually libertarians who love Wall Street in the day, but love their seedy nightlife after hours and want to protect it. At the end of the day, those types could care less if the guy down the street has health care.
So if you take the liberal definition in a holistic sense, Toronto is among the top liberal centres of North America, above New York or Chicago by far.