Interesting question. Here in the Great White North, we require a one-week OJI training course. It is probably Transport Canada approved, although the training mandate from them seems a little vague when compared with Europe and UK. To get on the next course you need only become next in line, and wait - anyone who wants the course seems to get it. Little consideration is given to experience, and some will get the course within a year of licensing (because everyone else in the unit has had it). There has not been any refresher or upgrade requirement, although the employer is considering introducing one. By the way, a recent report on training within this ANSP identified OJT as the area within which the most noticeable improvements to the training system could be made.