By acquiring part of Aer Lingus and developing a code share deal with them, they can use them as a way of increasing its foothold in the UK to better compete against Emirates and Qatar Airways there.
The
whole point of succesful sandpit based airlines going East from the UK is a
one stop service. DUB / GLA / NCL / MAN / BHX / LHR-DXB-XYZ.
Emirates would be
much more competitive from these airports than say ABZ-LHR-AUH-XYZ. The whole selling point of these guys is avoid the LHR experience. I cannot see Aer Lingus making money on UK domestic, even Ryanair gave up. From LHR, you're looking at ABZ / GLA / EDI / MAN / NCL realistically and NCL and MAN only have LHR links to feed BA, they would be loss makers on point to point. Feeding other airlines at LHR killed BMI in one sense as well, so I struggle to see what the logic or strategy would be.