I meant more the checking of messages than simply handling the device. Obviously moving it from a pocket to a door card or similar wouldn't to my mind constitute 'using' the device. But the law is there so that it encompasses the full range of uses of a mobile phone. The point is about distraction rather than making/receiving a phonecall and when I was a copper that was always how it was enforced. It's discretionary too: when I used to do foot patrol I tapped on many a person's window in stationary traffic whilst they were looking at messages. They crapped themselves, I told them off and they went on their way. I applied discretion because, let's face it, they're not endangering anyone by sitting there with the handbrake applied. It obviously isn't the same as driving with a distracted mind and without proper control of the vehicle.
I am not saying everyone applied it the same way I did but I know that generally speaking the people I know did. Nobody wanted to stitch up Joe Public, we wanted to punish those who weren't concentrating or weren't in proper control, 'cos they're the ones who cause accidents. It was no benefit to me to issue people with FPNs as a response bobby, so when I did they were deserved. Like the bloke with the Conti GT who couldn't afford a handsfree kit!
I can also assure you that most coppers would rather some easier way of contacting control than using their radios but often it is necessary and that's why there's provision to do so. The focus is on the car in front rather than what's for dinner and have I bought new shoes etc.!
re: speed camera. Pray it hasn't got film or the central ticket office has too many tickets to process and will bin it...