That sounds like it's the prosecutors, but that's not a valid talkgroup. Pros-Ops 11 is 54448, and the next whole talkgroup above that is 54464.
You are hearing a talkgroup with a status-bit of '+8', which equals 'DES Encryption talkgroup'.
My $.02 - turn off the status-bit feature on your scanner, so that any of the transmissions you hear will display as their 'root' base talkgroup. Leaving that feature on causes many a regular user to believe that they have found new, undocumented talkgroups on trunk systems.
Remember, if it's a Mototola system, the TGID has to be divisible by 16 (gives you a whole number after the division. 54456 turns out 3403.5).