BA have been trying to get off the LHR-BFS route for years. I remember the rumour going round some 10 years ago.
What you have to remember is that yes the route may be busy, even fill a Tristar at Christmas, but what is important is the ticket yield. Flights to Northern Ireland and the Republic of Ireland are low yield and have been for years. Dublin has had Ryan Air on the route for years forcing down fares, hence when BM started LHR-DUB BA pulled off. Now the low costs have started on London-Belfast pushing down fares.
Handling fees at LHR higher than LTN and STN. Theres a point when you have to stop throwing money away.
Its sad to see the route and any staff which go. Times are changing......