et al. have been looking into the mystery house near Kenny Hahn, here's what more I've (maybe) learned about it:
"There are approximately 950 acres that remain in private ownership, and on much of this area oil and gas are actively being produced and processed. Related surface structures include oil wells, pipes, water treatment and gas plants, storage tanks, buildings and service roads. Stocker Resources, Inc. has their administrative headquarters on site. Southern California Edison maintains a transmission facility at the southern end of the western ridgeline. The Holy Cross Cemetery property at the far southwest corner of the park site hosts some of the best examples of coastal sage scrub and riparian habitat; the cemetery uses this canyon to dispose of their plant waste material. A historic home built by the Chandler family exists on the western ridgeline and is currently in use as a private residence.