Lottery winnings aren't actually taxable here in Canada, but if a Canadian wins a US lottery the IRS might withhold some of it (30%?). DFS seems to be more interesting here. If you are a casual player, I believe winnings are considered a windfall and don't need to be reported. If you derive a considerable, sustainable income from it, then it's taxed as regular income (as far as I know).
My DK winnings shouldn't need to be reported at tax time to the CRA, and weren't withheld by the IRS either after signing the form stating no US business interests or whatever.