Just 10 years ago we had a fair amount of barge traffic on the Hudson carrying oil b/c no pipelines. If there is an arb, Americans will figure it out.
If Midwest Refiners pay up for heavy oil, it will get there. No matter how devious the plans, America will muddle along and figure it out.
Extend a rail line to shorten the distance. Once we start arguing about the minutiae like this, we are talking about a long war of attrition and I'll bet every day of the week that the US has deeper pockets and more capability in figuring out. Alberta well have a huge problem.