| I have had problems with my insurance covering certain meds and have had to appeal, but in my case that just meant complaining to CMS (Medicare) about the insurance companies decision. It can't hurt to appeal. I know that the Social Security Admin will routinely deny claims for certain kinds of disability but that a huge majority of those claims are in fact approved after appeal.
If you have a copy of the contract with BCBS, see what it says about investigational treatments. With any luck there might be a clause that permits coverage when there is medical necessity. Even if there isn't, a court might decide that it should be covered as a matter of public policy - if you wanted to take it that far.
Also consider contacting groups that advocate for diabetic rights. Don't know if ADA does that or not. | 
