I read the court's decision. It's online at
http://www.courtinfo.ca.gov/opinions/documents/S152360.PDF

The issue, according to the court, revolves around "medical" care. The statute says, “No person who in good faith, and not for compensation, renders emergency care at the scene of an emergency shall be liable for any civil damages resulting from any act or omission. The scene of an emergency shall not include emergency departments and other places where medical care is usually offered.”

The problem is that this section is part of a larger scheme which has a definition of emergency: “a condition or situation in which an individual has a need for immediate medical attention, or where the potential for such need is perceived by emergency personnel or a public safety agency.”

So the Supreme Court found that the Good Samaritan statute deals with providing medical attention when it says "emergency care." In the case in question, a woman pulled a crash victim from a car and left the victim lying on the ground by the car. The victim suffered spinal injury, is now a paraplegic, and is suing the driver of the car and the Good Samaritan, claiming both caused or contributed to her paralysis.

The Good Samaritan provided no medical care or attention to the accident victim, and the Supreme Court found that the normal law of negligence applies:
"Under well-established common law principles, a person has no duty to
come to the aid of another. (Artiglio v. Corning, Inc. (1998) 18 Cal.4th 604, 613;
Williams v. State of California (1983) 34 Cal.3d 18, 23.) If, however, a person
elects to come to someone’s aid, he or she has a duty to exercise due care." This means, it seems to me, that this case is not a change in how the law is applied generally, it's just a statement that the Good Samaritan law applies to medical care at the scene of an emergency, not to rescue efforts. (Three justices dissented from the opinion, pointing out some problems with the majority's decision, and those problems seem like, well, problems to me.)

But the major issue is that if you aren't providing medical care in an emergency, you need to exercise due care and not break someone's back rescuing them from a wrecked car. Whether our Good Samaritan did the damage is the subject of dispute, so that will go to trial.