862.8375 is the Everett control channel. Just about everybody got new radios in June, the only ones on the old system are Fire, Security, fuel dock and a few techs on the flightline.
Boeing is migrating to their P25 system. I'm not sure if the old 3A0 site is still up and running. I presume Matt wouldn't have responded with the frequency if it wasn't still up... but it's life is probably limited.