Denied on prior authorisation twice, approved on the third attempt after a peer-to-peer, and the only thing that changed was who was doing the talking.
Writing it up rather than posting a verdict, because a verdict is not checkable and the detail is.
Coverage criteria are plan-specific rather than insurer-specific. Two people with the same insurer and different employers have different rules, which is why "my insurer covers it" is not transferable information.
So the question, as narrowly as I can put it: what actually works on a prior-authorisation denial, as opposed to the list of things that sound like they should work. Not looking for reassurance. Looking for the part I have got wrong.