Another feel good law that will do little to protect someone from a lawsuit should they break the window of a car to "rescue" an animal. You will still end up in court trying to prove that the dog was actually in danger and there was no other option.
This law will embolden folks go looking for dogs in cars so they can break windows, feel like heroes and try to shame dog owners. The actually necessity of the "rescue" will be secondary to their crusade.
I often take my daughter's dog with me to visit the dog park and run errands. Some places he can go in with me, but others he can't. If I tell him to stay he curls up in the back and goes to sleep. Depending on the weather, I leave either the windows down, or the heater or air conditioner running for him.
If a dog is really in danger and no owner is around, go ahead and break the window and nobody is going to fault you. Just be sure, and not on a crusade or over reacting, or you are still going to be paying for a window.