Yes, Virgin, X-Country etc do recruit trainee drivers from time to time, but its far easier for them to recruit qualified drivers. This option lets them pick the best and obviously saves them alot of money and they have prodcutive drivers in a much shorter time frame.
I can't see TOCs outsourcing parts of the training for drivers to FE colleges. It wpuld cost them just the same, if not more and introduce another layer of complexity which the rail industry does not need. It would be resisted strongly by ASLEF and rightly so. Its just another way to feed the gravy train of privatisation, where large training organisations would make alot of money out of training thousands of people who may never get a job in the railway. In house training is always the way to go for roles that are safety critical such as train driver and conductor/guard.
ScotRail, like other TOCs, has a highly trained and dedicated team of trainers who know the roles inside out, how the company operate and the routes and traction thw company operate. The rules based part of the training, whilst classroom based, relies on the trainer being able to discuss real situations and signal systems and track layouts on the routes the trainees will work. A FE lecturer will not have that level of experience or knowledge of the railway that in house trainers do. Its easy to teach people to pass exams/assessments but alot harder, if not impossible, to teach people about a job/role if you have never done it. I also don't see railway experienced driver trainers leaving a highly paid job to move to the FE sector, where wages and conditions are poorer. In short, don't expect to see your local college in Scotland offering train driver courses anytime soon!