Bmach: EZPass is issued by each individual state...and here in NJ we get up to 4 transponders per (non-commercial) account.
Each one is marked for each vehicle. With me...the motorhome: the auto: the pickup and the motorcycle. (I must presume that with NJ EZPass one transponder will not work on any vehicle.)
The motorhome and pickup can pull "anything". Whatever is being towed, the license place must be registered.
I ended up calling the 1-800 number for the NJ EZPass and had them do the "classification" to enable the motorhome and pickup to tow "anything".
No problems in any state.