Since this is a non-standard type of transaction there is additional overhead to set this up, which acts as a disincentive for an employer or company to move forward.

A simpler approach may be to ask for wages instead, which could then be used to pay for training. But based on your question, you seem to be asking specifically if a company would be willing to exchange billable hours for paid training, thus I suspect the answer would be "possible, but not likely".