I actually called a number of local police departments, the California Highway Patrol, Alameda County Sheriff's Office, Department of Justice Bureau of Firearms, and my local District Attorney's Office with regards to UOC. DOJ and DA told me that they can't give any advice or guidance and to that I should read the pertinent statutes and consult an attorney for advice. The local police departments and CHP didn't have any definitive policies in place and were leaving it up to officer discretion (strongly erring on the side of "officer safety") on how to deal with open carriers. I was told by a Sgt. at the Sheriff's Office that they had a policy manual regarding what the law was with regards to open carry. I figured that manual might also have guidelines on how to deal with open carriers, but I was told that the public isn't allowed to have access to a copy of that manual.
Basically, I made an effort to talk law enforcement agencies, and I didn't receive much concrete help from any agency. I hope you have better luck than I did.