Where are the cameras placed to take a shot of the plate ? Most likely it is to the front of the car as it passes through the toll lane. If you are from a state such as SC, you only have a plate on the back of your car. So all these cams would get is a picture of a vanity plate or nothing at all.
The snapshot cams at a toll bridge near here take both: front (with an effort to capture an image of the driver) and rear also (with optimizations so the typical plate obscuration tricks don’t usually work).
No, my daughter visits me and she gets them in the mail, with a picture of her plate on the back of the car.