Actually we don't even have permanent placed cameras anywhere. So those signs would not do much good anyway.
We only use these minivans and police officers with speed guns. They never stand the same place more than 1 day.
So "fartkontrol" being ether a van with a cam or the police standing behind a bush or similar and catches people via speed guns.
we ofcause have plenty of these signs that reminds us that speed is dangerous.
We also have some "signs" that shows our speed. so if we drive too fast some lights blink. they do not send tickets. they just warn us of our speed. I guess this is our version of your countrys speed traps with warning signs.
Here is a picture of one of the speed signs:
the orange lights will blink if you go too fast.