Back in the late 90's there was a incident in Toronto where a woman was arrested for wandering around topless. She felt it was unfair that the laws were the way they were, so she did this to protest. One thing led to another, and the law was changed so that women could go topless in public.
I don't recall the precise jurisdiction of the law, ie, whether it was just metropolitan Toronto, or what.
There were some amusing incidents afterwards, such as strippers going topless outside their place of employment, in the hope of attracting new business. I think I even recall hearing about a woman doing the "squeegee kid" thing topless, but I might be mis-remembering that.
But yeah, if you're in Toronto and you want to go topless in public, go for it. It's probably worth noting that venues such as movie theatres, malls and restaurants may have their own rules, so don't be a complete twonk about it if you decide to go topless.