Hmm, there must be a way it's just that we don't know what it is. Sounds like a challenge to me. First step, ask Mercedes (but don't hold your breath!)
It would be nice to think so. However I suspect this functionality has been removed because the use of speed camera POIs is illegal in some countries. My guess it that it has gone for good. As far as I know, several other European manufacturers haven't offered this function for some time - certainly it's not present on my wife's BMW nav system (equivalent in other ways to Comand).
I've seen no official word from Mercedes about this. If you'd like to follow up, perhaps via your local dealership, then by all means do so.
Regards,
Malcolm