Correct FFF. The ground vehicles will be using UHF radio not VHF as Aircraft do. At EGCC their audio is patched through so that both the Aircraft and ground vehicles can hear each other (at least on 'ground')
Airband communication is always SCS (single channel simplex) in my experience. Although a long time ago - the seventies - two aircraft of my acquaintance had an ancient Collins valve Tx/Rx setup that was switchable to Double Channel Simplex ie. transmit and receive on different frequencies, I think we had to modify it out ! The aircraft were ex Aerolinas Argentinas.
Under non atmospherically enhanced conditions a rule of thumb for the extension of line of sight for VHF is 1.23 * Line of Sight distance if memory serves.