I don't think you are permitted to have a separate ground on the sub-panel unless it is bonded back to the main panel ground. We had two buildings that were fed from different pole transformers and they still make us bond the two building grounds together.
So what's the difference between two buildings fed off different transformers, and 2 separate homes? 2 adjacent homes don't have to be bonded. Now I suppose if you had other wiring going back and forth (CATV, phone, etc) between buildings - but that's different.
In my case I'm feeding the detached garage from my house service entrance panel - so I get that. That was part of the problem - the quoting electrician (actually my wife did this without asking me!) said that the garage could be grounded separately. And I didn't believe him!
In NEC 2005 it was still permissible to have a separately grounded sub-panel in a detached building like a garage IF there were NO other conductive paths between the two buildings (phone lines, coax cables, metal water lines, etc.). In NEC 2008 it was changed that the sub panel in the second building in addition to having its own ground rod(s) must also be bonded to the main panel with a ground wire (4 wire system). I'd be surprised if there are many jurisdictions left anywhere that are still using NEC 2005 as their basis. So I'd get another quote from another electrician
The other thing I've thought of is to have two operating positions - a "primary" position in the detached building for contesting etc, and a "secondary" position in the house. Maybe with a fat run of heliax between them. But my understanding is I still have to bond the two positions together and to the service entrance. So that complicates things even more.
Presumably the two stations would share or swap antennas, or have an interconnect feedline(s) as you noted.. For that reason alone I would want to bond the grounding systems together between both locations, this is true whether even if they are fed by separate electrical services or not. It has as much to do with the lightning protection aspects of the whole system as it does AC power system safety.