I certainly feel for you Mac84.
Just 3 days before my family and I were supposed to make the long drive from Michigan to Pennsylvania to have my Gamma Knife brain surgery with Dr. Lundsford, his hospital (UPMC) called very late in the afternoon to deny my treatment even though my insurance BCBS had me pre-approved with a written letter. Dr. Lundford's personal nurse even sent me an unsolicited email saying I was "all good to go" on the insurance front. To this date, no one has ever apologized from Dr. Lunsford's office for all the anxiety, waste of time, and replanning they caused. It still leaves a bad taste in my mouth.
Anyhow, as you know, MRIs are very expensive. I hope you can work it out in your favor with BCBS, as obviously most everyone with an Acoustic Neuroma will need a one-year follow-up MRI regardless if they have had treatment.