I think anyone who has flown under the Tac C2 in OEF has earned their hostile fire/combat pay, tanker or not. Just going out there every day and not getting killed by ATC or some UAV pilot who doesnt understand how to set his altimeter properly should be enough to warrant the pay.
I guess if I had my way if your shop is not manned 7 days a week, no hostile fire pay for you (Just keeping it real for our maintainers)