Damage caused by unregistered vehicles in an underground car park

Hello tosmamen, my vehicle is in a collection garage, where there are also several summer vehicles, i.e. vehicles, with seasonal approval or partly no registration plates, one should probably become a vintage car there. Who is liable for damages, if such a vehicle causes a fire e.g.? With a season registration mark then there is no more protection and with longer not registered vehicles anyway no more? Would then the PHV of the holder (if available) jump in or stick the owner with his private assets. If then 50 vehicles are connected, plus damage to the building substance, the private assets may not be sufficient. How is the situation here, nothing has happened so far, but better you know beforehand and can possibly go to the people with appropriate arguments or you reassure me, because who would pay.