I assume it would be worldwide, but when you go 'off the tools' for a period to work in training, procedures/simulator development,etc it is a given that you will work some extra hours for free.
It is swings and roundabouts. When in the centre you work your rostered hours and get paid for any additional hours. You work 24/7 shiftwork and you must work your rostered shifts.
Out the back you may have nominal shifts but you can turn these into 'florist' shifts ( i.e. you make your own arrangements) work on your RDO and have a day off somewhere else if you wish. You are expected to complete the work, if this entails you having to work a 10-12 hour day to fit into what else is happening so be it, and you MAY get the time back somewhere else.
If you are training someone and this entails you having to start earlier to prepare the simulator and stay back later to debrief the trainee, so be it.
Being ATC, we always seem to think the grass is greener elsewhere. Some of those out the back believe it is easier to just to work the rostered shifts in the room, whilst some of those in the room are jealous of the non 24/7 florists. Having worked both it is six of one, half a dozen of the other. The best way is to make sure you don't spend too long 'out the back' and lose sight of what ATC is about. The longer you are away from the console the easier you remember the 'real' job as being.
You run into problems when you get people who have been years away from controlling who come up with 'great ideas' on paper that will never work in the real world.
Sorry about the thread drift. Good luck to the Belgians.