I think you'll find that BT make lots of money renting telephone lines to the airport operators for use between the control tower and the Tx/Rx site. These might be copper lines but they may have been replaced by fibre.
At one time at Farnborough, our main Tx/Rx site was at Ewshot, about a mile south west of the airfield. For a short time, our techies tried a microwave link rather than RAE having to pay BT lots of money (they even rented cables to operate traffic lights on the airfield from BT) but it was quickly found that heavy rain, not even torrential, was sufficient to block the signal, so we reverted to cables.