What I find amusing is that anyone should find this surprising.
Read the FT article and you'll find alot of 'shoulds','coulds' and 'mights'. Once again it is one of a plethora of 'plans' that go through the rumour mill. This one possibly has legs but it remains to be seen if the customer booking through flights wants to start his/her journey on a low cost airline. Continuity of a feeder product is important in these cases hence that, plus the difficulty of rapid turnaround ops through LHR make it a little tricky.
Personally I don't see this taking routes but, possibly, enhancing routes through Gatwick.
Time will tell but, to rain on Wonkers parade, it is not an unexpected ploy by those of us who have the ability to see beyond BA's hallowed halls and will be dealt with accordingly, like adults.