BA and others using integrated or structured modular suppliers are simply contracting out the training they are neither equipped nor wish to provide themselves. Contracting out of specialist services, including training, is common in all industries and is not indicative of discrimination.
Aviation is unusual (but not unique) in that the entirety of training is generally paid for by the student at his or her own financial risk, and this is simply down to market forces generated by the numbers of wannabes wishing to fly. However standardising the provision of training is important to a large organisation like BA who find it very difficult, time consuming and expensive to themselves standardise new pilots from too many different training backgrounds - which has to be done before they enter type and line training.
Ideally, I'm sure BA would like all its ab-initio pilots to come from a single source. Trouble is, no school these days is going to put all its eggs in one customer's basket - the income ramifications of even small changes in demand are huge. Therefore, organisations like BA with a large demand (at least currently) for new pilots will need to contract with more than one training provider, and may even, at times of peak demand, have to look elsewhere. But that causes the standarisation issues I referred to above, and won't go down well either with the training department professionals or the accountants.
I repeat: it's not about discrimination, it's about quality control and standardisation.
Scroggs