Yeah I think it's mostly the same in Germany... any tools (be it an app on the phone or active radar warning devices) to warn you about speed cameras are VERBOTEN!!!! same loophole might also work, thoughSuper illegal? Why?
I did get a sort of warning when I turned them on saying 'this may not comply with all local laws etc don't sue us if you get a ticket' but I thought this was meant for France where all sort of warnings are banned.... amusingly there is loophole in the law that allows for warnings for "Points of interest" as long as you don't specify it's a speedcamera....
Oh yeah, it's rather nice that you've kept that market design alive! And it does make sense... we used to have a similar thing for people who heat their homes with electricity (night storage heaters), but I think it was always only used for that and it's not actually all that feasible to get these tariffs anymore. there's now heat pump / EV charging tariffs, but those are usage-based rather than time-based (so the heat pump or charger has a second electricity meter) and only reduce the power grid fees (up to 7ct/kWh), not the base energy cost. Still good, but you end up having to pay for the second meter.