Now my lucky guess would be that the RFID Reader Shell datagram URL would be "lcif://RFID/(something)/1.0" if the same rules are used as before. FunShell API says this (something) is the "feature" used.
Personally I think Nokia should support more open standards on these cases. If anyone has any more information about how the shell works or if I'm wrong in this then he/she can correct. Of course if Nokia itself can give information about the protocol it would be nice.