And often surrounded by land I would wager the government owns, which could be used to build the transfer stations upon. Maybe even a susbsidised incentive to get companies on board, so they don't have to spend their own time and capital acquiring land.
They could do brake and other inspections there too.
Weight and dimension check stations would need to be considerably enlarged to allow for load handling facilities.
If it has space for a parking spot it has enough space to transfer a trailer to a different rig. No one is talking about unloading anything, it's just lowering the legs on the trailer and unlocking the fifth wheel to let the autonomous truck pull away and back the new truck up to it.