Mike,
Is White's Hill located south and west of Malone? Near Parishville NY and Potsdam?
It's probably worth noting that I hear traffic on 163.725 quite well over a large swath of western Vermont but I don't hear much on it in the Massena area. Massena seems to be covered on 168.850.
Today I was in northern New York and signal-stalk/close called 165.925 carrying digital noise with a CTCSS of 151.4 near Chateaugay. It definitely was not P-25 encrypted voice. This was some other kind of digital encryption. It also seemed to be simulcast on 163.775 also carrying a CTCSS of 151.4. Both outputs were extremely busy and, yes, both carried a CTCSS of 151.4. Any ideas? Sorry, I'm not NAC-capable. Maybe someone who is can tune these in to see if they carry a NAC code as well.