Two screenshots to finally prove you what I'm trying to explain.
This is Digital Design's EDDP, in the first screen, the small Van is following the vehicle paths, because it's CUSTOM made for the scenery (it has EDDP logo, so it's clearly not default ), so it must use its own custom method to follow that path, WITHOUT using the AFCAD.
In the 2nd screen, the baggage belt loader it's a custom object provided by the scenery (it also has an Liepzig airport livery, even if it's not easy to see), so it's following the vehicle path.
The blue snow plower truck, instead, it's a *default* Ground vehicle, so it uses the AFCAD and, guess what, it's running over a taxiway!, exactly like a GSX vehicle would, because default ground vehicles require Vehicle Paths in the AFCAD, just as GSX ones, and the airport doesn't have any.
I hope you are satisfied now and please, don't you think we should KNOW of ground traffic (and its interaction with the AFCAD ) work, having done this for the past 7 years ?