I stand by my original response here - you cannot bill for something that's outside of the scope of a license. But I think you're asking a slightly different question here now: what is within the scope of a license and what is within the scope of a physician's specialty and training are two different things. For the former question, you need to go to the license board and regulations of the state where your provider practices. But for the latter question, you're correct that there is leeway within a physician's practice to make determinations about what procedures or services are within the scope of their training and what services are covered by a license but which need to be referred to someone more specialized due to the limits of their training, and I agree with you that this would be a peer-to-peer question and not something that a coder or non-clinician should be trying to answer. This is more a question of medical ethics and practice.
But as I mentioned in my previous post, there's also the question of whether or not it is appropriate for a physician to be reimbursed for services that are being performed as part of a training program. When a provider bills for a service, they are certifying that this was a service that they personally performed and for which they are wholly responsible. If in actuality it was service that was performed under the supervision of another provider who was paid to oversee it, this could potentially put the provider in conflict with their payers' requirements and contractual obligations.
This is an unusual situation, and these aren't easy questions to answer, and I think it unlikely you'll find regulations or documentation that addresses this situation specifically. In your place, I'd be advising my provider to get professional legal advice from a specialist or attorney in your state of practice who can properly advise on the risks vs. benefits that the provider could face in making as decision like this.