I still believe that if you took all the macho BS out of the equation and started with blank piece of paper, then a unified cross base deal would be achievable. As you have said, the savings have been made.
The savings are coming from Mixed Fleet being on separate contracts as a separate fleet.
Based on BASSA's track record, BA would never be able to agree an integrated approach to the LHR fleets that would yield the savings BA was looking for.