They really are used mainly for parking, in bus lanes, on double-yellows, outside schools, in restricted bays. They'll be looking for vans loading on LL in the bus lane, of which there are many on a weekday. They can film people driving in bus lanes, but it's harder to convict as the perpetrator has to be filmed driving past the sign at the start of the bus lane and has to be seen driving for more than 10m inside the white lines of the lane. Otherwise it's not a sound conviction.