On the server game we discovered that it is possible to use other players stops on public (city) roads without permission.
It is an interesting feature, I hesitate to call it a bug, but it is worth knowing.
Is it possible to disallow it?
Even if you can pass (or put a waypoint), you have to disable stopping there.
It will easily interfere with other players.
EDIT:
It may be possible to prohibit loading.
The road is public, so I would say this is sort of payback :)
This is not a bug - this is intended. The idea is that a player should not be permitted to put something private on a public road. The whole point of a public road is that one cannot exclude other players from it. The same applies to waterways.