I concur, you should be able to listen to the radio as long as it is in inventory and turned on.
Communicating, though, should require it being in hand at the moment the message is sent out.
Actually, another thing that would be interesting to have in-game is a separate "band scanner" item, giving a percentage chance to detect radio transmissions on different channels.
On the other hand, with VoIP being a far superior communication method... yeah.