Any 2 fixed points in the pictures can be used as a secondary check to corroborate the speed reading, the white lines simply make it a bit easier for this to be done en masse.
Whilst that's true, wouldn't the partnership need to send someone around to measure the distance between those two fixed points and then provide proof of those measurements?
There is a requirement for a secondary check method to be available, but the method is not specified. Photogrammetry can be used without painted lines being present.
When the lines are not present, it depends on local policy - some may send out the NIP, some may not.