Personal testing of plate covers resulted in a simple conclusion. The angle of almost all permanent cameras and laser guns connected to cameras is too little for the 'polarized' effect to work. Every laser photo I have seen has been about 300ft or greater, and as some 'plate' manufacturers say 20 degrees plus, you are talking the camera has to be an absurd distance from the road side.
One night, stop at a permanent camera and measure the angles, you will then know why you were caught. I did this at a few sites and at those angles measured the camera would of bust me every time.
They are implementing a toll system onto our existing highways here, where you pay per kilometre you drive and so far, it is the only permanent camera setup I have come across where a polarized plate would have a great enough angle to work.
What we did years ago, but I aint telling you this, was to take blue and white insulation tape (same colours as our letters) and put legs on to the p's making them r's and visa versa. But if you stopped, the penalties are serious. I spent a night in jail and stood in front of a judge and as from that day, I now have a criminal record.