Yes, I agree with Heather - it seems to be clinic specific and up to the doctors (and sometimes your insurance company) how hard you have to push to get a vest -- how it was explained to me is (from our doctor) that there is no clinical evidence to prove that one form of CPT is better than another, but compliance certainly goes up with the vest and therefore a person can get improvement because they are doing the CPT on a more regular basis.
We had to file an appeal for our daughter to get hers - my son's went through very quickly - you just never know what's going to happen with insurance companies -- the lessons I learned when trying to get my daughters approved may have helped to get my son's approved ... like getting a letter of medical necessity fro the doctor to submit at the same time, rather than waiting for them to ask for it (delaying approval) or denying the claim altogether.