It's a good piece of publicity altjhough slightly unfair given BA hasn't got £20 million and if it had, it would come out of taxed income whereas Sir Richard would pull it off a long string of dodgy offshore stashes (why else offshore?).
I'm not sure what's particularly different anyway. BA and AA have already got all these slots so it's not a question of pinching anything off Sir R. If anything they would reduce services thus creating some space.
The issue must be through-ticketing and I can't see why Virgin can't come up with a way of competing with that proposition.