The GE powered aircraft were not liked by BA, I'm sure I'll be corrected if I'm wrong but they were always planned to be traded in at a later date, hence the zzz reg.
The GE engines were underpowered for BA's requirements, so these original a/c being 14 years old would not good business for any long haul airlines to purchase them, however parting them out would provide a significant return for any purchaser.