A fairly good description of what happens at the end of your training with regards to getting a job is given in a cadet blog on the CTC website.
"The responsibility of placing cadets from the hold pool has recently changed hands, and is now handled by a branch of CTC called Airline Recruitment Ltd (ARL). There were a few teething problems during their take over of the pool, but all in all they're ok to deal with. They send out a monthly update e-mail giving the current job situation and any opportunities that are on the horizon, and there seems to be a lot of activity at the moment which is great news for anyone finishing soon! There is now basically a rule of 2 in the hold pool. This means you can turn-down up to two opportunities, be unsuccessful in up to two airline assessments, or be in the hold pool for a maximum of 2 years. After that, you're on your own! I think as there's so many people coming through CTC at the moment, they need to implement some rules or the hold pool will be huge"