While recently I was at the factory and going over a list of changes I hoped to add to a new 2552, one of which was to add a switch to switch the cab radio from the chassis battery to house battery power. Don, who I believe is the manufacturing manager, was adamant that this was not an option as the radio is controlled by the ford computer and they were concerned this would cause problems.
It is not clear to me why the computer would care about the power line but it was clear PC wasn't about to change their position.
You can get around this a bit, possibly, by using the battery boost switch to supply power to the chassis battery if you are concerned about running down the chassis battery and/or get a volt meter to plug into a lighter plug to periodically check on the state of charge of the chassis battery,
..Mike