Tank trucks exist, they're just more expensive, which is why pipelines have been on the agenda. We also have upgraders that make heavy oil light - I've seen some desulfering plants in person (yes, I'm in this picture, if only geographically). It's a distillation away from being petrol (and heavy/heating oil and asphalt), and the main cost of shipping is petrol, so the economic case is really just driven by the need for it at the other end.

Meanwhile, in Ontario a part crosses the border multiple times on it's way to being generally saleable as a car, and would rack up 25% every time as the policy is currently proposed. You're right, Alberta will be in the shitter economically, but we're not the most vulnerable, let alone the most vulnerable by far.