That's the rub with Glen Valley CYA and the surrounding areas. Only those using it know the frequency. Transiting aircraft wisely monitor 123.2 or 126.7 and encounter near misses with aircraft working the periphery of that CYA. Been there, done that.
FWIW, the frequency is listed on a piece of paper stapled to the wall at the flying club in Chilliwack - that's about as official as it gets.