414.5625 Mhz Continued

Over the last few years I've seen reports of, and heard myself, some encrypted P-25 transmissions on 414.5625 MHz. Reports have come from Houston, Boston and Charlotte, NC of the same type traffic. The agency is unknown and traffic is, so far, entirely secure.

Initially the traffic reports had a P-25 NAC of N168 being heard, but lately the same frequency has been seen until N169 as well. Also have seen reports of what might be the same agency using 414.7500 MHz, also with a NAC of N169. 414.7500 MHz has traditionally been known as a US Postal Inspectors frequency and it is assigned to them nationwide. However, it is not an exclusive assignment. The various branches of the Department of Defense have some limited allocations of the same frequency, as well as the Bureau of Prisons.

My initial guess it might be one of the DoD Special Investigative agencies, or a DoD security detail of some sort. I have run into various DoD security details on various UHF channels over the years.

UPDATE:
 I have been told by reliable sources that the frequency of 414.5625 does show some allocations to the US Postal Service in the Government Master File, but nothing else. So this could be some new assignment or some sort of special use by the Postal Inspectors. More as we find it!