I've got a zumo 660, it does warn of fixed speed cameras but I can't say if it's only on pre-programmed routes, I've never really thought about it, although I'm fairly sure it just notifies you if you have the map showing but not on a planned route. Maybe I'll nip out and check tomorrow as I've got a camera just down the road.
I also have a Novus Rider speed camera detector
http://www.novus-gps.co.uk/Novus_GPS_Rider.php
The novus has free updates for life (of the unit!!!!!) and seem to update their database quite frequently. Whereas the zumo has four updates per year. Therefore the novus is going to be more accurate and includes specs cameras that monitor average speeds on motorways. As these chop and change fairly frequently around roadworks the Novus is more likely to be more accurate, more often.
Neither of these units are capable of detecting mobile cameras that are in use although they both notify you when you are in a known mobile camera use zone.
Hope this helps.