Sorry Ian, CB was deregulated in 2006. No license required.
MSA Radio - No way. Thats real pointless bureaucracy territory. A real radio messed about with by people who like rules.
Proper Amateur radio - probably the way to go if you are really into radios and want to communicate a lot, all the time, but not cheap and you need to pass an exam...and like rules.
For actual mobile comms, anywhere, anytime - Iridium satellite mobile phone.
For green-laning maybe once a month ? Probably a hand-held CB is the way to go, so you can walk up to the problem/stand by the gate and still talk. No exam, quite cheap, takes 0.4 seconds to learn how to use.....