According to the assembly rules (if I am understanding them correctly), amendments like that are considered out of order and can be shot down with a majority vote:

"92. An amendment to any bill, other than a bill stating legislative intent to make necessary statutory changes to implement the Budget Bill, whether reported by a committee or offered by a Member, is not in order when the amendment relates to a different subject than, is intended to accomplish a different purpose than, or requires a title essentially different than, the original bill."

http://www.leginfo.ca.gov/rules/assembly_rules.pdf

That being said, it seems that typically nobody in the legislature ever cares to challenge it. I saw it happen for another bill this session too (an AI bill that became something about commercial fishing).