It would be helpful if you can provide a source for this. Mr. Edgar has presented a LOT of useful things but appears to have gone about it in the wrong manner, eg. I believe he was helping a motorist who was defending a S172 prosecution. Also his website (formerly
www.notsoaccurate.com ) was quickly filled with what appeared (to me) to be unsubstantiated rants which would make anybody think he was a crank, whether they were true or not. Somebody also pointed out that he is a
Vexacious Litigant which is not an easy thing to attain, although if his rants about the "old boys club" were true then this would make such a things a lot easier!
Anyway, I believe somebody on PePiPoo has got a lot of information about the Gatso via. the FoI which might provide some information. I think a Field Strength Meter would be used to measure the levels he was talking about, they are quite easy to obtain and an experienced Radio Amateur would probably have one and be willing to do measurements for free.
Gareth