Unfortunately, it is my suspicion that there are many masters runners - age groupers in general...who are cheating. It is more so they can train without getting hurt, than to run really fast 'open' times, but it's cheating nonetheless.
I think you can look at anyone who has been running for many years, and then is suddenly approaching or beating their open times as a 40+, and not breaking down under the strain of intense training, and 'wonder.' It's sickening, but it's the reality of it. They don't test at the Master's level, and many people who compete at that level use it as their chance to finally get 'their 15 minutes.'
I don't know about California, but I can say it is prevelant in Colorado. Those of you who follow the sport closely can pick them out. Of course, there is no proof, so no accusations will hold up, and the accusers will be seen as bitter or jealous. But I can tell you, as a former elite, you know which Masters are cheating, and which are legit...anyone who understands running progression will tell you the same.