Cannot say I blame Sir MB for delaying whilst the LHR infrastructure is so poor.
When BMI do take on the others, it will need a superior service as well as keen pricing to compete effectively.
Anyone remembering the competition between BMA and the BA shuttle between LHR and GLA/EDI will also remember the lesson that BA were taught then. I would suspect that Sir MB remembers only too well and that is why he is prepared to wait.