California has the same system (Fastrak) throughout the state, but different regions sell their own toll tags (with their own accounts).
Here in northern California, the
new tag is a stick that's about 1.5" x 1" x 6". They
recommend that you put it on your windshield, but will also accept a tank bag, jacket pocket, or glovebox. Mine is mounted in the glovebox, on the side of the tool compartment.
On the Golden Gate Bridge, I usually get billed by the tag. On the other bridges, I usually get billed by plate. If neither the tag reader nor the camera detect you, you've had a good day. 🙂
[edit] Apparently Fastrak in southern California comes in a
windshield sticker now. Interesting idea, but not sure why you'd bother since you can be billed by plate anywhere, and you risk being billed as a car if you use a sticker in an Express Lane.