The mission that is using the city waste truck instead of the alaskan is because it's used in coop, the main reason why this was changed is due to the the "corpse" attach points on the alaskan. The function for this is more or less the same one used for carlos when he's being drug around. The dlc changed how that function worked, more or less more attach points and other things would need to be entirely redone to support this. While I can't speak for tervel directly, it was briefly mentioned as not planned during testing. I however hope this is revisited in the future and implemented.