166.4625 MHz Las Vegas TSA?

I've been hearing numerous transmissions in the area of McCarren Airport in Las Vegas on 166.4625 MHz, P-25 with a NAC of 001. It appears to be the Transportation Security Administration operators working with the full body scanners at the security checkpoints. The operators are apparently in a different area from the scanners themselves, and are calling out when the subject being scanned is clear and if there are any anomalies detected by the scanner. The transmissions are all simplex and low-powered.

The frequency is assigned as Treasury Common as well as DHS Common in many federal agency radios. This frequency and P-25 NAC is known to be Channel 13 in the standard TSA channel plan. I have heard similar traffic in other locations, specifically at the Tampa airport during the Super Bowl last year.

169.6000 MHz NYC

I've received some reports of a mystery P-25 frequency active in the New York City area.

169.6000 MHz, NAC 169 was first reported as being a patched simulcast of the Federal Protective Service UHF channel, 417.2000 MHz. I was first wondering if this might be the reason some FPS vehicles have been seen with VHF antennas on them.

But further reports have come in that say this frequency has been heard repeating various NYPD Citywide channels and Newark NJ PD channels as well.

The frequency itself has been used by many different federal agencies, including the Department of Agriculture, US Coast Guard, Customs and Department of Energy, to name a few. It's unknown who is using this frequency for what purpose, but further monitoring may give us a clue.