For anyone playing along at home, they Keystone Pipeline is already complete, running from Hardesty, Alberta to Houston, TX. The Dakota Access extension shortcut would have allowed the pipeline to enter the US through Montana instead of running all the way to Manitoba before entering the US, meaning that the pipeline would sooner reach lower latitudes be easier to access, inspect, and maintain.
So this argument - that it’d have to be run in trucks instead - is entirely baseless.