Agreed it is stupid to sit at a red light in the middle of nowhere when you can clearly see the route ahead is clear. Glad you mentioned the threat of a hidden police car. It tempers behaviour for car drivers but seemingly not for cyclists. That said you simply never know what type of copper you might pass or what mood they might be in and where you would stand or if they would see things your way, after all the law doesn't always see eye to eye with common sense.Maybe it's a London/country thing. Sometimes, it just seems silly to sit in the middle of nowhere waiting because a machine tells you to (in RSA they are called "robots", which I quite like).
The one thing that always stuck with me regarding the police and their enforcement of law is that it is largely on a whim. Shortly after I passed my test I was reversing the car around a corner and I had taken my seat belt off as allowed for such a manoeuvre when a police car drove past, stopped and one copper leaned out the window and proceeded to have a go at me for driving without a seat belt and how dangerous it was... I was gob smacked and was shot down for trying to explain I was reversing with a patronising 'The shortest journeys are the most dangerous'. More recently I was sitting at traffic lights behind a police car, I could see a cyclist behind me approaching the red lights at a fair pace and as expected he shot past the police car and through the red lights. The driver of the police car waited for the lights to change and pulled the cyclist over. Knowing one of the police officers I was later told that he was fined (I don't know the specifics of the offence/fine)... another time and he may have been ignored or let off with a warning.