Technically, CHP can give you a ticket if you use the FasTrak lanes without a FasTrack transponder, even though their computer system has no problems billing your account by license plate.
I've heard of it happening online, but never seen them pull somebody over personally.
Since earlier this year, they are taking an alternate approach with the Golden Gate bridge, and have switched to electronic only tolls. So either you have fastrak, or when you drive across they photograph your license plate and mail you a bill. No more pay by cash, or differentiated lanes. I could see that becoming the norm.
I drove across the Golden Gate Bridge a few months ago with no idea that this was going to happen - last time I was down there, they still had a normal tollbooth. I was in a borrowed car with Washington plates. If they'd had a normal toll booth I'd have paid, but with the system set up the way it was, I don't think they had any way to get revenue out of me.
I was also very confused the first time a drove across without the toll collectors. It felt like I was doing something wrong, and was going to end getting a ticket.
Do you know if the person you borrowed the car from got a bill? I'm curious if they are only able to bill California plates, or they have a national database of license plates.
At least the Port Mann Bridge in Vancouver, which uses the same license plate camera only style billing, has a database which they use to send a bill to your insurance.
I've heard of it happening online, but never seen them pull somebody over personally.