After mentioning that I haven't seen a Burr Oak, I ran smack into this one at a local bird sanctuary and farm animal display. And look where I found it!
There are 27 trees, mostly imported, along a stretch along the shore of Lake Ontario, honouring the 27 Canadians who were killed on 9/11.
So now I've seen a Burr Oak. It appears to be a species of Red Oak, with the pointy lobes on the leaves. There's at least one in Ontario.