Regarding west coast feral bees:

Yes! There are alot of feral bees here. You may remember I got started beekeeping in September by taking a feral hive from a friend's wall. Some other beekeepers here are busy removing bees all the time.
In any case, I work at a lab near San Fernando Valley, and I always notice alot of bee traffic. I put some honey out there and within a half hour I had bees coming from 3 different directions. I followed one of the paths, and in short order they started checking me out on their way to the honey. I decided to back off at that point, you never know around here where there might be an aggressive hive. I was thinking of putting on some gear and looking for the bees on a day off. I may have more time to find where they are at and determine if they are too "mean" to mess with.
I am keeping my bees about a mile from the lab, along with 25 or so other beehives owned by another beekeeper. I suspect these feral bees may be swarms from the beeyard that have settled in the nearby hills. The bees in the yard have become aggressive in the past, and required re-queening the entire apiary to calm them down (chasing vehicles, unworkable temperment, etc). I'm a little concerned about crashing around looking for bees here, but I might have a go at it sometime.
As to why they are here, who knows? Is it because they are working all year and never have any "downtime" during the winter?
The person who's house I removed the bees from reports that they had been there for years. I did not have the knowledge at that time to check the feral drone comb for mites, and the bees have been treated with strips since then.
Steve