It's hard for me to explain but it's there. For the most part, it's easier to pick out the people from Ontario compared to Western Canadians but after a little while, the Western Canadian will "give it away" so to speak. There's just a certain way they sound that is so subtle. Determining Sara Olesky's nationality would take a few minutes of listening to her (Western Canadian) but there's no denying she is in fact Canadian just by how she sounds when she says certain things.
Canadians from Ontario say aboot, owt, organeyezation among other words, it's more pronounced. Of course, they probably don't think they have an accent just like I don't think I have an accent but if I were to go to say England, they would say I have an accent and vice versa. Watching a hockey game and listening to a guy talk, if he didn't have an obvious european name, for the most part, I can tell who's canadian and who's american without looking at their place of birth. It's the sublteties