While researching something else I came across this, and it's the first I've heard about it. Not only would the Global Hawk refuel another Global Hawk, but they have a role reversal... the tanker will join up from behind with the probe.. while the 'tankee' or reciever will be the forward aircraft with the hose and drogue! This will extend the flight time of the GH from 35 hours to 125 hours.
Nice article on this, and check out the "refueling mishaps" video linked at the bottom of the article.. its got the infamous Sea Stallion event but also several others I'd never seen before. Enjoy!