A few months ago I was told by Mark Frost, then head of transport at Hounslow council, that, no, cameras can't have dual (or multiple) purposes. They might also be installed by different authorities: TfL is responsible for ULEZ cameras; many of the ANPR cameras will be LB Hounslow or LB Ealing cameras (depending on where the cameras are, of course!).
Joanna Biddolph ● 1855d