Caught a new one for me in the LA area last week. I was working up in Burbank and caught a transmission on 172.1875 MHz, N167, the FBI with a possible bank robbery. The dispatcher was looking for any unit available to cover. Radio ID matched the FBI.
Previously, I have caught traffic on this frequency using a NAC of N195, reportedly the CBP IWN repeater called BROWNFIELD 2. It certainly is possible for them to re-use this frequency, and the FBI use is probably north of the LA Downtown area.
Also, just updated TSA information for the Bob Hope Burbank Airport. You can find these updates in the TSA Frequency Updates section on the main blog page: http://mt-fedfiles.blogspot.com/p/tsa-frequency-updates.html