Normally under PR, you'd increase the number of MPs per district, which means that the size of the ridings would have to be consolidated. You might have, for example, a district that now would be, say, Montreal versus different parts or particular cities in Toronto. Normally you would have to have multi-member districts to have any sort of PR system. That would be the easiest way to do it, but it would depend on the boundary commission and how they would think through what would be a natural constituency and what would be the conventions of drawing boundaries.
On August 23rd, 2016. See this statement in context.