The type you describe is unusual here in Norway. They exist, but they're even signed in a special way. I'd hazard a guess that they make up <5% of cameras. Most cameras here by far are induction loops that trigger photos. From memory, it seems to be the case in the rest of Scandinavia + Germany too. But I could be wrong.

Either way, the public auditing procedure I outline could apply to time-between-two-photos-cameras too.