First note that the Atlantic refineries export most of their refined product, and for the amount that they sell in Canada, they have been buying the same amount of Canadian oil from Newfoundland and the West.  Essentially, the oil they import is just refined and exported.  

As for Ontario, about 80% of the oil refined there is from western Canada and the rest from the US.  Over half of the oil in Quebec is from western Canada, a quarter from the US.  With line 9, imports fell 25% in Quebec last year, and they can now source 100% NA oil.

Imports increased 33% in Western Canada last year, 100% of it from the US, and they now import 1.5 times more than Quebec does, 20% of total oil imports.  But it's mostly diluent and light oil used in mixing bitumen into WCS or dilbit so again, most of it is just exported again.

And Nova Scotia and Newfoundland don't care that Alberta doesn't buy diluent and light oil from them because they make money exporting it anyway.  No reason to fuss about it.