They are identical.

BAA is the subsidiary of BA which is used for LHR-HKG-TPE in order to comply with the PRC's rules 'prohibiting' direct air links between the PRC and Taiwan.

As far as the PRC was always concerned, HKG was included, so while CX flew HKG - TPE, they could not fly into China. Similarly with BA.

It's a fiction, everybody knows it'a a fiction, but it gets the job done.