We started using it. You cannot actually use any number following the DCM prefix. We were told we had to select something in the 30xx or 31xx range since that is what the FAA accorded them. When I asked if they were seeking approval for additional numbers they said no. The benefit is that in addition to anonymity, the DCM identifiers were also blocked at the vendor level. There were some issues early on since Flightaware was somehow able to tie up the callsigns to tail numbers and customers were pissed. The FAA is also now looking at the legality of a service provider allowing use of their identifier. Whether or not BARR gets reinstated, it's at least a temporary solution.