Nailed this one down for good last Friday evening. It is 866.8375 186.2 PL. They were doing down firefighter/RIT training in Leesburg. The channel was clearly IDed as 6-Ocean.
As I said in this thread, I also hear 6O on 900.7000 MHz.
It's not used very much, however, today (Sunday 10/8) Ashburn Volunteer Fire & Rescue will be holding it's Fall Open House (1-4pm)... we make use of 6O for various operations during the day