Why on earth would BA engineers use her to train on ? They may as welll get them trained on tridents or some other ancient bit of kit that have no relevance whatsoever
Many airlines, or at least those who still run their own in-house training, use retired aircraft and engines for apprentices to cut their teeth on. Whether or not that's the case with G-BOAB I don't know, but even if it isn't you would be surprised at just how much of the structure and systems of a 40-year old aircraft is still relevant today.