You only have to pay taxes if you and the canadians report it. And if the Canadians aren't going to be reporting the winnings (I don't know if they do, but you should find out...), why should you bother reporting it yourself? Consider it a freebie!
...Yes we can delve into the ethics and morality of not reporting this and I don't intend to threadjack, but I just wanted to put my point out there