It does need aircraft and crews, but that is only a problem if everything is done in one go. IAG (and BA) have lots of options available to them:
1) 777 deliveries - 3 coming soon.
2) 747 returning from the desert - I think there are 2 more still parked up.
3) 787 deliveries starting 2013.
4) 380 deliveries starting 2013.
5) Defer 767 withdrawls due when 787's arrive.
6) Defer 747 withdrawls due when 380's arrive.
7) Juggle routes and a/c with LGW.
8) Use more IB aircraft on London - Spain.
This could be really interesting. Remember you also only have to use slots 80% of time to retain them so with some juggling of schedules and a/c around shorthaul you can spread them out.