"Right equipment" is probably very load bearing. Wouls need a very high gain directional antenna, not sure if a camera next to the road has the space to pick this up from a moving car.
https://www.zebra.com/us/en/products/rfid/rfid-readers.html?...
Although, as I understand it, Flock itself is mostly just looking for Bluetooth, BTLE, TPMS Sensors, and Wifi devices.