I just caught some traffic on a VHF channel with some radio techs regarding receive sites and signal strengths as well as a radio interface bridge. The conversation was on 173.1625 MHz, N156, and I only heard one side of the conversation most of the time, but did hear a couple of replies from a field unit. I also heard one person ask if they were on the "APX" radio. APX is the Motorola radio series that features multi-band operation in a single radio.
This joins the frequencies of 170.6500 MHz and 170.9500 MHz that are most likely VHF DEA channels that have been heard in the Southern California area.