I’m guessing BE have cashed in their LGW slot? Operating a route with no competition would seem to be a far better use of those LHR slots. The eventual start of Crossrail will also make a vast swathe of London and the east plus Reading and others to the west far more accessible than at LGW.
I’m guessing the chap that said the remedy slots were reserved for domestics is correct rather than the one that specified ABZ/EDI.