My source in true PPrune tradition, is purely 'off the record', but the business needs of a robust and dare I say it, uncaring BA management are dictated by minimising complexity.
The BA Flight Operations hierarchy seek to have pilots of a brand loyal nature from the off. Employing those who elect to accept the T's and C's without bitterness and hollow self entitlement might ensure that sentiment. With that in mind it seems the business case of opening up recruitment to LGW to the Baby pilots is under consideration thus making the guaranteed employment of Mainline Airbus pilots less likely.
Ruthless, I know, but BA want desperation from the BMI community in order to fulfill their aims of having a compliant and unbitter future ex-BMI workforce.