They are eligible, but you need to become CARB compliant to register in CA. That will cost you quite a bit of money (i've heard up to $10,000). The facility to do this is in Santa Ana...
I explored the option with my last vehicle. The process is very opaque with a lot of smoke and mirrors. The owner of the company will not even provide you a real quote, he just writes the figure on a piece of paper and hands it to you. I chose to sell the truck and start over.