What part of English Canada? In Alberta or Ontario (the parts I've lived in, though I was pretty young when I lived in Ontario) I've literally never seen a calendar with Monday as the first day of the week that I can recall.
I don't honestly care much what people consider the beginning of the week, I try to avoid ambiguity in planning as much as I can anyways for other reasons (this Sunday vs next Sunday for eg.) but I have been tripped up by an unexpected Monday-first calendar in a webapp.
If someone says "let's meet the 3rd week of April" and you say "ok, let's do Sunday", do you really mean the Sunday in the 4th calendar row?