I'm Canadian, my gal is American, and we've both worked in both countries under various immigration statuses. So I've been around the block a bit. As I understand it, you're an american citizen who resides in, and plans to continue residing in, the US. I would expect:
1) You'll get a temporary, provisional license based on project need. It won't be a real, permanent license in the normal sense. It annoys me thoroughly when states do this to me (talkin' to YOU lone star state).
2) The provisional license will be very easy to obtain owing to your US qualifications and the North American Free Trade Agreement.
Might wanna get on that while there still is such a thing as NAFTA. I've been through this in a few provinces and states but not Ontario specifically.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.