While traveling through Los Angeles International Airport (LAX) today, I noted that the Transportation Security Administration (TSA) agents in the Terminal 2 checkpoint had Motorola APX-900 radios with them instead of the BK Radios that they have been using for some years now.
I put one of the radios in my backpack into searching the UHF federal band and quickly came up with some encrypted traffic on 406.7375 MHz, with a P-25 NAC of N031.
There may be additional UHF channels in use at LAX, but it will take some time to find them. But this frequency seems to be common for all TSA locations so far. The repeater input is 415.7375 MHz.