We asked him to tell us more. He wrote back with some detail (edited for space).
My wife is a dual citizen of Canada and US. Our children are also dual. Our oldest is a sophomore at McGill in Montreal. Our youngest is deciding between Boston University, University of Toronto, Queens College in Kingston, University of British Columbia, McGill in Montreal, U of M Twin Cities and UW Madison.
McGill allows about 10% of their students to be from the States, however being dual they are considered as Canadians so more likely to get into the school.
Total cost for McGill is about the same as the UofM for Canadian students. Currently there is a ~$1.25 Can for $1.00 US, so it is about 15% discount compared to the U of M given all the fees to exchange into Canadian dollars. Last year it was the other way, ~$0.95 Canadian for $1.00 US.
Canada's making it easy these days to explore college options. It may not be for everyone but given the potential savings it's worth examining.