MarkD is quite correct to point out that KC135 longevity stems from early lifecycle acquisition. The KC767A has nearly 20 years more product development behind it than the elderly ex-BA767-336 aircraft; it also carries 14.5 tonne more fuel and has a real glass flight deck based on the 767-400, unlike the BA aircraft. Whereas the A330-200 has over 50% more fuel available than the B767-336, Airbus industry-proven FBW and capabilities which comprehensively outclass any 767.
The A330 wing already has hardpoints and it is a straightforward task to modify them to carry an AR pod rather than an outboard engine.
Whilst the A330 is bigger and heavier than the 767, even operating from a larger aerodrome hundreds of miles further away from the Air Refuelling Area than one used by a B767, it still offers far greater fuel offload volumes.
The alleged 'dirty tricks' concerning the USAF's acquisition won't do any favours for Boeing, following on as it does from the recent missile scandal. Whereas Airbus have a product which sells itself without needing any 'help'....