Shaka, as a "off-shore" controller who came to Canada from Blighty, I too heard some of the stories you refer to (and have seen them posted on this site as well).
Now, I can only speak for Winnipeg Centre, but controllers not checking people out to "protect their overtime" is pure garbage. Overtime can be nice now and then (especially in Winter when it's -30 out), but there's only so much you can work without adversely affecting your health, your sanity and your personal life. Summer is too short round here to be stuck inside (ain't wireless internet just the best thing
)
We as sector worker bees don't really have an influence over people getting hired or not. Recently there has been a change within Nav Can regarding IFR ab-initio training.......it is now done regionally at the centres (this is a different topic alltogether). The program is still in it's infancy.......
As to actually checking somebody out, there is a QTP (Qualification Training Program) that must be adhered to that outlines the training process for live OJI, the level of performance that must be met at the end of each phase (normally 20 days per phase, but that depends upon speciality) by the trainee. And at the end of the day, the person giving the nod is going to have to work next to the guy or gal they are giving the licence to.
The instance you refer to regarding moving to different units is known as "Seniority Bidding" (kinda like the airlines). You can apply/bid for a move up the ladder to a new position based on your seniority (you can go backwards once in your career, for instance a move from YYZ Terminal to YHZ Terminal or YVR Tower to YWG Tower). Now, I profess I don't know all the ins and outs of it, but with respect to training there are return rights on placements where you could request to go back to your old unit (and requalify) if things weren't quite working out. And sometimes it's all very well bidding on a new position/to another centre, but if the speciality you're trying to get out of is short staffed, then chances are you won't be released. I'm sure somebody else who know the whole thing a little better can explain it better.