I think it would actually be better if they refuse to integrate with the large apps, and instead use the green activation as a feature to entice people away from those apps.
It hardly seems like the Flemish government are going to create an app that's a serious competitor to Google Maps etc. Even just reaching something reasonably functional for driving directions would be an awful lot of work.
There are some good open-source apps for driving directions. The big problem with those apps is often the lack of a source for live traffic information, but the government probably has something for that already, so hooking that up into an open-source app should be quite effective. Shouldn't be too hard to advertise an app if it means you see more green lights on your journey.
If Google Maps had broadcast your individual(!) position and navigation intent to the local government people would scream about privacy. I'm not sure it's better when a local app does it.
