This subject is a pet hate of mine that goes back a few years. I remember when I doing a 2 day Cuplok conversion course at one the (can't name it) CITB training facilities. There where a group of Prison Guards there taking Basic II as they were trying to keep everything 'in house' to minimize the risk of bringing in an external contractor.
Yeah, I could see the point from a safety and security point of view, but Prison Guards aren't in the business of erecting and dismantling scaffolding on a daily basis. Therefore it would become very easy for them to become complacent in a profession they are not time experienced nor time served in, putting themselves at risk!
No one likes working the nicks and with SGB we had our fair share of them, Rampton being one of the scariest! But again, it's was taking away our bread & butter.
As for rehabilitating ex-cons, truth be told none of us are angels in this profession to start with anyway and there are some decent folk get locked up for some of the stupidest things (sympathising with football and drink related related crimes here) and do deserve a chance as it is nigh-on impossible to find employment with a record nowadays.
With regards the issue of certificates, a definite no as I fail to see how you could gain any experience inside. There is also the quality of training, I don't know of any CITB NVQ certified Instructors that operate out of the prison system? Job placement I would strongly agree with. Tickets are to be earned in the real world, on site!
Cheers,
Phil.