I used to live there - and used to fly across the Santa Ynez mountains
on nearly every flight. Never saw a thing, nor heard of any incidents.
I once came across an explanation that it was a route used for cruise
missiles - launched offshore by ships or aircraft, and destined to
impact at the China Lake NWS. I also read that the missions, by policy,
always occurred at dawn, and that the missiles were required to be
accompanied by a chase aircraft (that presumably had the means to
destroy them if a conflict or other hazardous condition developed).

That route has existed for a long time. It is entirely possible that
the activity it was created for has been long abandoned - but the Navy
neglected to do away with it. It likewise took the government a long
time to do away with the prohibited area over Ronald Reagan's ranch
(also in this area) after he left office.

David Johnson