I found a bit of information regarding Belgium's motorway lighting policy, which helps to clarify some things. Belgium is a divided country that speaks two languages. It is broadly split into two regions, Flemish (Dutch) and Wallonia (French).
Since July 2011 there has been a new motorway lighting policy in the Flemish region. This has seen a considerable amount of motorway lighting permanently switched off, with another considerable proportion dynamically switched. Dynamic switching is a number of things. One aspect is part night lighting, switching off in the early hours. Another aspect is to keep the lighting switched off, but to switch it on depending on traffic volumes, weather conditions, the presence of roadworks or incidents. There is relatively little all night lighting on the mainlines of motorways. Slip roads are retaining all night lighting, as are sections of motorway where junctions are less than 3km apart, as are ring motorways around cities where traffic volumes are particularly high, and sections of motorway which are of a lower design standard.
To give a rough example of the extent of lighting switch off, prior to the policy being implemented around 84% of Flemish motorways were lit all night. Since then, this has dropped to less than 48%, or around 18% all-night lighting and 29% dynamically switched lighting. Apparently it saves the authorities around EUR 2million per year. I'm not sure what rate they are charged.
Below is a map of the Flemish region showing the status of motorway lighting. Green means all-night, orange means dynamically switched, and red means permanently switched off.
Interestingly there are motorways on the map which supposedly have all night or dynamically switched lighting, yet when we visited were unlit either due to failed lamps or the columns being chopped at the bases, so even where lighting isn't permanently switched off it doesn't guarantee the lighting is in full working order!
Meanwhile, in the Wallonia region lighting is retained, but lighting in the central reservation is part night. This applied in the Flemish region from 2007 to 2011.