I wish I could give some advice, but, it is I gather not just an Ontario thing, but a NATIONAL issue. The bain of concern for many IMG's who go to the US for their residency is that the vast majority of residencies are less in the amount of time compared to their Canadian counterparts. This is not a rule put in place by the provinces, but rather the college (RCPSC) and their related specialties. I think that vis a vis, the situation is not the same for FM as many programs in the US are 2-3 years and it is 2 in Canada.
I know that many of my classmates who went to the US are finishing up in the next few years (I graduated in 2003) and will have major problems getting back in as a full-time attending specialist. As you may already know, once you are finished your residency (on what is probably your J-1 visa), you are booted out of the US only to come back to Canada for a minimum of 2 years (unless you receive the evasive H1-B visa); not fun to not practice in Canada while either: a) doing more "work" as a fellow at a cheap salary rate, and/or b) knit all day 🙁
That is the reason I didn't choose the US route and knowing that my school of medicine had one of the best probabilities for matching in Canada compared to all other IMG schools also sealed my fate.
I wish I could give you better news.
NOTE: as I have eluded to in another post, we had a discussion with one of the head personnel of the CPSO (Ontario). He indicated that if the USMLE 1,2,3 are all done before coming to Canada, they are seen as EQUAL exams when trying to practice in Ontario for registration purposes and thus you don't have to do the MCCEE/QE1/QE2. I don't think it will be an issue as virtually every Canadian who has gone abroad has had to write the MCCEE to get their "Statement of Need" letter from Health Canada to get into a residency in the US. As he also indicated, when one province does something, all follow suit in due time.