Tom - just to clear something up - some Subaru alarms suffered interference if they were close to an antenna. Can we rule that out in this case?
You can reprogramme using the keypad, so if you need to replace the fobs you can - problem is I dont think the transponder is a separate unit.
here is a picture of the M30 alarm you can see key fobs, sensors, siren and ECU but no separate transponder unit