I believe that superchargers along the TransCanada Hwy from Calgary to Southern Ontario should be a higher priority than supercharging I94 through North Dakota and Montana (given that I90 is already supercharged).
It also does not take a fully connected network for superchargers to have their biggest impact, for example it is more important to have a supercharger location in Virden, MB than to have a supercharger in either Regina or Winnipeg.
I also think that Tesla Motor's current plans for Prairie superchargers are suboptimal. For starters, I think that the three supercharger locations currently slated to connect Calgary to Montana could be better deployed to: (1) Cranbrook (connecting Calgary to Coeur d'Alene supercharger and the I90 network); (2) Medicine Hat; and (3) Swift Current. Add one more supercharger location In Virden and then you can leave Winnipeg after work, crash at a Regina motel with a level 2 charger, and then drive to Calgary the next day in time to watch the Jets play the Flames on a Saturday night.
I think you need to re-check the distances involved and the numbers of Superchargers. Calgary to Crankbrook is about 390km. Calgary to Couer d'Alene is about 640km. When Tesla puts in Superchargers, they're forward-thinking and look for year-round travel, so a Supercharger in Cranbrook is not going to be enough. They'd need to add several different Superchargers. The time for Calgary, AB to Seattle, WA via Couer d'Alene, ID compared to via the TransCanada Highway seems to be a wash, and for travel to Portland, OR it cuts about an hour. On the other hand, connecting Calgary, AB to Butte, MT would provide a much more direct route to large areas of the USA, cutting multiple hours, while also "finishing" I-15 in the USA.
That connection is also more populated than the route to Couer d'Alene through Cranbrook. To me the connection to Butte looks like a much greater benefit.
The distance from Winnipeg to Virden is around 300km. Again, they'd need multiple Superchargers for year-round travel.
Manitoba is more populous than Saskatchewan and Winnipeg, MB is a much more populous area than Regina, SK or Saskatoon, SK, so it also makes sense to focus on connections to and from Winnipeg. Tesla plans to connect it to the USA's network via Grand Forks, ND and Fargo, ND. That connection would provide a faster route to Toronto than through Canada (ignoring border checks, of course), as well opening up travel to US destinations.
Once they have the Calgary, AB to Butte, MT connection, and the Winnipeg, MB to Fargo, ND connection, then Tesla could begin to add eastwards from Calgary, and westwards from Winnipeg and each new Supercharger would be of greater value than it is now, because those Superchargers would be more connected.
Also note that Tesla's 2016 map shows an additional Supercharger near Sudbury, ON, and one in Northern Michigan, which would then also put Tesla closer to making the connection across the north of Lake Huron, and then connecting Winnipeg to Eastern Canada.
Stop being Canadians and rock the boat! (Or drop down and see how much our Northern plains look like your Southern plains on your East-West trips).
