I don't think Maxis even exists as separate entity anymore. Aren't they just a small division within EA now? EA kept the brand name because Maxis used to be good, but it doesn't mean anything today.
Maxis has a separate studio in Emeryville (by Berkeley), where Spore and SimCity were developed. Maxis isn't exactly small, since The Sims franchise has been responsible for a large share of their profits: A few years ago EA reorganized into three parts, and The Sims division was one of them, but I don't know how they're organized now.