Many automated tolling systems use forward and rearward oriented cameras to capture plate images. Some are smart enough to match up ownership of your trailer and tow vehicle, while others will double bill you. If you borrow someone else's trailer or tow vehicle and hitch it to yours, you have a better chance of getting double billed. A friend of mine was triple billed for the same bridge toll because he was hauling a car on an open trailer and cameras picked up three different license plate numbers.
Automated systems have also failed when cameras are used to count the number of axles. Just watch what happens when someone tows two vehicles on a flat bed trailer behind their truck...