Halfwayback... true enough, both bmi and Virgin fly LHR-Mumbai; in the recent round of licence applications, both bid for 7 flights a week. At that point, they were indeed competing for the flights available.
However, both were awarded only part of the flights on offer. I don't know if they fly on different days, or if there is an overlap; in this case I believe it would be in a merged company's interest to continue to operate all seven flights. There is even an argument that the customer would benefit, by having flights every day of the week, without having to change carrier.