Wouldn't Tesla be collecting real world data now since Kingston, Comber and Woodstock are all open? That information probably settles the east / west volume discussion.
Yes, Tesla will be collecting statistics. But the number of cars using Kingston tells you very little about what traffic is going east from Toronto; I expect that the majority of traffic there does not go through Toronto. My main point is that you can't make a general claim about the 401 west of Toronto vs east of Toronto, the traffic volumes vary drastically in each direction depending upon where you are (primarily, depending on distance from Toronto). Further, the notion that there is more traffic going to Windsor than to Montreal is not borne out by the statistics collected by the Ministry of Transportation of Ontario - if you want to make a simplistic comparison, there's actually greater volume at the Quebec end than the U.S.A end of the highway. Also, the road itself is 4 lanes both east of and west of Toronto; that's not a differentiating factor. So making this broad claim as a justification for the placement of Superchargers is not supported by evidence.
I have no horse in this race, as the saying goes, but it seems crystal clear to me that the next biggest need in the vicinity of Toronto is Cobourg. The route to the east IS important, and is underserved at present, with the distance between the Toronto service centre and Kingston supercharger being larger than is ideal. The route to the U.S. (which I have done, btw) is more than adequately served with the Superchargers at Woodstock and Comber, and there are lots of Superchargers already in operation or under construction in Michigan. Heading toward the U.S. south of Lake Ontario will also be dealt with adequately by the Supercharger in Buffalo. Another one in the vicinity of, say, St Catharines, could come in handy, but I don't see it as a high priority.
Meanwhile, Vancouver Island, with a population close to one million, and notable tourist destinations on the west side of the island and population centres on the east side, has no Supercharger and no plans for Superchargers. Likewise, the east coast will be underserved for the foreseeable future.
Just a bit of perspective for you.
You guys are all discussing where you can put multiple Superchargers near Toronto, while a significant number of routes could be opened up with one Supercharger on Vancouver Island, and one or two in New Brunswick and Nova Scotia.