Are you talking about the fuel trucks on the ground? Should be at least one located on each apron, and and one to serve each group of 15-20 aircraft. The ground vehicle routes between aprons need to be linked to keep the vehicles off the taxiways and runways.
Or are you talking about in the air refueling? Which is more a concept of operations question and it would be best to address that on the Military AI Works forums - http://www.militaryaiworks.com/
@ PawPaw's house - near KADS, Addison, Texas, USA