Tesla launched a bunch of Ontario Superchargers in March, so it's not fair to say there has been no construction this year. But it did come to a screeching halt after that. Aside from finishing some long-delayed Quebec chargers.
So obviously the contractors are available. They've already built stuff.
I'll also point out that they've pretty much fully built out the New York network, and many of those are in the wasteland of upstate NY, so they must largely exist to support Canada/USA travel. As such you could consider them adjunct to the Ontario/Quebec network.
My guesses:
(a) Site selection / permitting delays galore, or
(b) Tesla's Supercharger team built out the absolute minimum necessary network, declared victory, and left the country.
Given the total lack of news, I'm kinda leaning towards (b) at this point.