This article describes the southern end of the road as Churchill rather than Sundance. If so the road will NOT connect to the rest of the North American highway network and it will still not be possible to drive to Nunavut without using some other mode of transportation on the way.
This probably does shave considerably off the cost, though, and there are train tracks running to Churchill, so for freight it would function just fine.
Also, seems another benefit would be the construction of power lines along the route, dropping electricity prices in southern Nunavut. The road would then be needed to service those lines.