Van that detects if drivers are holding a mobile phone trialed in UK

The UK will test a system that uses photos of drivers of passing cars to detect those who are not wearing seat belts, or are holding phones in their hands.

Detecting the use of a snoop-phone while driving is a good thing, in itself, because that practice is dangerous. But I wonder what else these photos could (and will) be used for. Will the state use them to identify every driver by facial recognition? And ever passenger, too?

There should be technical safeguards in the system to ensure it can't be used for this