Out of curiosity I looked thru the FCC database for non-public services licensees for all of San Luis Obispo and Monterey Counties. There were no "Hearst" found there (as you know) and nothing that stood out as something tied to Heart (e.g. cattle company, vineyard and so on).
As you may know, Hearst owns a lot of land inland, bothin SLO and Monterey Counties. When I've been on some of those properties I've never noticed antennas on ranch vehicles and certainly no marked security vehicles. That's not to say they don't exist, just never saw any. On one occasion I spoke to a Hearst employee in there main office for the area about communicating a certain issue among ranch personnel, and they just sent an email.
Of course I don't know your itinerary, but from my travels most of the Hearst properties are pretty well locked up with gates and fences. Consequently it would be difficult to enter an area where you wouldn't be welcomed anyway.
As an aside, I was along the south coast road (off of Nacimiento-Ferguson Road) earlier this year. Some great views and a few dispersed camping areas there.