I believe the end of April is going to be the crunch time for T5 when most of the longhaul flights move from T4. At the moment about 40% of BA's pax are using T5, & the system is just about coping with a 20% of these planned flights culled !!!!. So when the rest arrive what then???
If the story is true that BA is to be heavily fined for all the disrupted PAX, (say £1000 x 10000 pax pd = £10M pd my best guess) then it would be cheaper for the airline to shut down.!!!!!!