Also given T2 already seems to be full, how exactly were they planning on getting BMI in there. Seems we avoided a whole lot of bussing when BA bought out BMI.
It's academic now, but a way would have been found. BD would have been by far the largest tenant of LHR-2, and would have played a vital role in feeding longhaul Star Alliance flights.
Perhaps some of the smaller, shorthaul, or less connection-orientated Star Alliance carriers would have stayed out until the second phase was built.