I've had no success either. I followed the order to the letter. I also am wondering if anyone else in Canada has had success (more recently than these instructions were originally posted). I did update "timeZoneId":"Canada/Mountain" with no difficulty.
After having no success with the directions/order Alex posted, I tried updating distanceUnits":"METRIC" and ,"temperatureScale":"CELSIUS" manually as a matter of curiosity to see if I'd get a "200 OK" (which did work). I tried playing with a bunch of other parameters as well, all with no success. It didn't choke when I changed "supportedLocales":["en-US","en-CA","en-GB","de-DE"] (to include en-CA) but it didn't seem to add any enhanced functionality.