The cops haven't asked for it because the cops are planning to railroad your boyfriend into jail. Often, when there is a physical altercation, the first person who speaks to the cops is treated by the cops as the victim. If the neighbor spoke to the cops first, the cops are treating the neighbor as the victim - which means that the cops will try to avoid looking at any evidence that could clear your boyfriend.
Make sure that your boyfriend gets an attorney, and that the attorney subpoenas the videotape BEFORE the videotape is erased.