The hack is to connect it to an LED light that everytime it recieved the ezpass who are you signal, it would light up with a "
moo cow" sound to indicate it was read.
His hacking wasn't too avoid the tolls, or commit fraud, but to identify everywhere his tag was being read [location, date, time] and not at toll roads/plazas.
PopSci, published his method for anyone that also wanted to do the hack.
https://www.popsci.com/article/diy/ezpass-hack-covert-scanning/
He posted everything he did and the "authorities" never went after him & still 8 years later no effort to go after him. My guess is that if the authorities want to pursue him, there first request will be to return the device and that he won't return that device and just claim it went lost/destroyed.