I think there is some overlapping here between what is generally agreed is a training bond as oppose to an agreement to pay all or part to wards ones own training.
The bond, as I have always understood it, is an amount that you agree to pay the company that train you on a new type should you decide to leave them before you have completed the agreed period of return of service, probably between three and five years. Provided you complete the time period no money changes hands.
Paying for ones training is a whole different ball game and is a fairly recent abomination but brought about, in part, because people have offered to pay to get a job.