I also went through the scheme on the "old" system. We got around £500 per month plus allowances which were pretty good. It works on both sides - I got a type rating and 300 hours of experience (and a job at the end of it) and the company got 6 months work in exchange for paying for my training/ type rating.
It does not deprive anyone of a job. The airlines like it because they know the people have been through a selection and have passed the training. The pilots like it because they are not bonded to the company for a disgusting amount of money for a number of years, but are free to do what they like after the 6 months (but virtually all are offered jobs at the end). If BALPA do not object to the scheme then I guess they agree.