Fool me once, shame on you - fool me twice, shame on me.
The only reason for the inclusion of Airbus for a tender on a commercially based tanker would be, as the only competitor in the market, would be to try and drive the price of the Boeing tender down.
Bioeing know it, Airbus knows and Congress knows it.
If the invitation to tender offers to pick up all the costs of the losing bidder it might be worthwhile*, otherwise why waste time and money?
* I say might - it would draw a lot if engineers away from areas where the profit margin might be far greater.