Isn't this just a straight forward exchange?
Most likely, but the question is "Why now?". The RAF took several RAAF exchange personnel on the Waddington AWACS squadrons in the lead up to the Australians buying Wedgetail, and it would make sense to have a cadre of trained RAF crew should we buy Wedgetail (much as we did at Geilenkirchen while waiting for the Sentry to be built). I would expect the number of "exchange" personnel to grow should we eventually buy the aircraft.