There should be a procedure for obtaining 911 records, this includes the audio and the print out of the number from the call. Here there is a procedure which must be followed, if there is a written request that portion of the tape is not destroyed after 30 days. It was put in place after it was kind of/sort of/oppsed found out the prosecutors were delaying some charges past the 30 days to let tapes be erased as a matter of SOP because there might have been useful defense material. (name of witnesses, informents)
If no such procedure exists they may have to go to court to get an order directing the material be preserved until further order of the court.
I read a post from him today, but I don't know what it was dated. He said his lawyer was trying to get the 911 records, but they were (as you said) most likely calling it an internal matter to delay long enough for the tapes to be destroyed.