BA are happy to punt the Glasgow London market out of Heathrow going forward, this was I believe the main reason for the surprise resumption of the historically loss making GLA-LCY.
The frequency of the Shuttle has fallen from a high of 14 daily to the present freqeuncies to allow for more long haul growth at LHR as this is where the money is made. Not wanting to lose long haul feed but keen to lose frequency means BA brought back LCY.