First of all, BA did not imply or say that slots were easy to come by, they said that it is possiblefor new entrants to obtain slots at the airport, and Virgin Atlantic are a good example of it happening.
Secondly, it is not up to BA to provide slots to other carriers, and it never was. New slots are obtained from the pool, either due to greater efficiency or when a carrier vacates them.
This just reminds of me of those occasions when a six year old makes a silly bet that no-one takes him up on, and then goes around shouting that he's won.