I was coming down the A5 between Oswestry and Shrewsbury last thursday (15 jan ) about 11 am, there were two camera vans on a bridge above the road just before you get to the fixed camera at Shottaton.
The 10% + 2 mph would apply to cars because of possible variations in the speedos but trucks speedos are calibrated to actual road speed so therefore the 10% might not apply.
I was following a traffic police car on the A141 last year in my car and a couple of cars in front of that was an artic doing 56.The police wernt a bit bothered and turned off a few miles down the road,so maybe its pot luck whether you get done or not.