CA - to answer you directly...you can certainly try but once the insurance co finds out that your treatment relates to a work-related injury they'll try to get reimbursed from them and the WC carrier will deny it then they may come back to you.
Some other questions though, have you settled your claim by Stipulations? If so, what %?
The insurance carrier has some requirements on it when a med provider requests authorization for medical treatment. Once the request is made in writing by fax or mail the carrier has 5 days to respond. Usually they'll send thru their Utilization Review provider who will review the request and may even contact your dr to get more info if not available on the face of their request. If they don't get it or get enough they'll give to a Dr to review for non-certification. To delay, deny or modify a request for med treatment must be done by a physician. If the Dr. agrees and says their requests is non-certified (for whatever reason) the carrier can still authorize but will usually deny the request.
The dr's office can submit more infor for reconsideration with 5 more days and another decision will be generated on certification. Also, if you disagree with a decision regarding medical treatment (usually non-certification) you may object with 20 days of the Ins Co's denial and get a Panel Qualified Medical Evaluation to resolve the issue. OR...if you've already had a Panel QME you'd go back to that Dr. for an opinion on the care requested. If you were represented by an attorney you'd go back to an Agreed Medical Evaluator.
The law has changed and the primary treating physician no longer has the presumption of correctness. Now guidelines called ACOEM - American College of Occupational and Environmental Medicine are deemed presumptively correct. They can be rebutted but only by peer-reviewed, evidence based medicine.
Either way, you have recourse. Hope this helps.