I have always said the "powers that be" should have a HUGE advertising campaign on the use of mobile phones while driving. A bit like they did with seat belts years ago.
There would then be no excuse when they are caught.
I think we all know that it is against the law to to use a mobile phone whilst driving. However, 'driving' includes making/receiving a call whilst stationary at the side of a roadway and the engine is still running. The vehicle Must be safely parked with the ignition turned off.