You must have been receiving the Santiago Peak to Frazier Mountain link that is on 166.5625 MHz. Frazier transmits back to Santiago on 164.9125 MHz. Frazier also transmits to Santa Ynez on 164.9125 MHz also and Santa Ynez transmits on 166.5625 back to Frazier. The remainder of the linking is via 400 MHz frequencies. Santiago used to be down linked to the San Bernardino Federal Interagency Communications Center, the Monte Vista ECC, and South Ops in Riverside with 415.525 MHz and up linked from those locations with 411.525. The Angeles NF used to be linked the same way when they were in Pasadena and later Arcadia, but now that they are over the hill in the Antelope Valley, I'm not sure how they are linked. They might be like the Inyo NF and are linked via the state's microwave system. Santa Ynez Peak was linked to the Los Padres NF dispatch center via the same UHF frequencies. The dispatch centers in Porterville (Central Calif. BLM and Sequoia NF), Visalia (Tulare Unit CDF), Clovis (Fresno-Kings Unit CDF and Sierra NF), and Sonora (Stanislaus NF) were connected to Frazier in the same way. I'm not sure of San Andreas (Tuloumne-Calaveras Unit CDF) and Mariposa (Madera-Mariposa-Merced Unit CDF) use the state microwave or are linked to Frazier on the 400 MHz frequencies.
You may be able to copy the 415.525 MHz Santiago Peak downlink from your location. I know I pick up 440 MHz ham repeaters in the northern San Fernando Valley on my mobile when I'm down there. Its a bit scratchy in the northern part of the valley, but then I'm using a hatchback lip mount with only a 17" dual band antenna.
The up link frequency shows 411.525 as the plan I have is much older than 2005, the year the federal government began mandatory narrow band and changed the spread between the up and down links from 4 MHz to 9 MHz. So if 415.525 is still the down link then 406.525 would be the up link. Recently, (as of 1/2008) the federal government's National Telecommunications and Information Administration (NTIA) Redbook contained wording to the effect that the down link is to be the lower of the two. If that change has been made to the South Ops Net, then 406.525 MHz would be the down link and 415.525 would be the up link. It is possible that this change has not been made yet as it has only been about 1-2 months since the UHF linking system was updated here on the Inyo NF so try both 415.525 MHz and 406.525 MHz for awhile first.
The other possibility is that a completely different pair is now currently in use. If you don't hear anything on 406/415.525 then try searching the entire 406.1125-410.9875 MHz portion of the UHF band and you may get something. The up link used to be repeated on the down link, so you should be able to hear everything on the South Ops Net if you can, in fact, receive the UHF downlink. If not, then I would suggest you try the 164.9125 Frazier to Santiago link. I don't think you will be able to copy it from your location as you are probably in a shadow for Frazier. I know I can't receive or key up any ham repeaters on Frazier from the northwest portion of the San Fernando Valley. In addition, the VHF signal from Frazier to Santa Ynez and Santiago on 164.9125 is shown in the plan as being horizontally polarized so you may not get very much penetration or ground level signal in the shadow you are in. Although it is not specifically addressed in the plan, I believe the down link is transmitted from Santiago Peak on an omni-directional antenna.
If there is anyone located in the L.A. Basin (from Oceanside to West L.A. and out to San Bernardino and Riverside) that can try the above 400 MHz frequencies and see if they can copy South Ops, I would appreciate it. This is a good frequency to listen to during fire season, although computers and phones are quite often used to relay orders between the dispatch centers and South Ops. Even so, the last time I was down in southern California and heard this net, the traffic certainly added to my understanding of a number of incidents being worked on the Los Padres, Angeles, and Cleveland National Forests.