Truckers are paid per mile and have a driving limit of 11 hours per day and 70 hours per week. Having an autopilot take over for part of the trip could substantially increase the ground they can cover in a day.
Or do you think they will benefit from resisting all forms of automation? I doubt it will slow down the eventual outcome, which is pretty much set in stone already. But maybe I'm wrong.
Then you could have a small number of vehicles, or small companies could pop up to serve this role, that refuel automated trucks that run out and stop driving outside those automated routes (if this is even a concern).
If you are eliminating 80%+ of trucker salaries, you have a lot of money to work with.