alt Hacker NewsSeems about as effective as could be though. By the time you see them doing it, it's already cleared up by the time you pull out your phone to video it to use as evidence. So this is pretty much acknowledging that it would be ripe for abuse if it had any actual consequence.
Patiently collect multiple (say 3) independent reports of the same plate. Have the police show up for a surprise physical inspection (free of charge naturally). Track the sources and targets of reports to watch for any abuse.