In the beginning, a call meant an almost definite police response, and one where they were confused as well as thinking their lives might be in danger, (never mind the fact they also liked to screw with us and sometimes still do.)
Now that the police, and portion of the public which has a double digit IQ and some form of attention span knows what OCing is and that it's legal, we have just about no problems anymore from 911 calls. I believe a few years ago MOC even worked with police agencies to develop a protocol.
As far back as 2008, in the wake of the boston market incident, Sheriff Bouchard and I discussed educating dispatchers, which he then did, and after that forwarded his departments information on OCing to the rest of the sheriffs departments in the state. How much the rest of them did with it at that point I don't know, but I do know that the OCSD educated all their cops and dispatchers, and I haven't had or heard of a problem out of them since, at least in regards to OCing.