I don’t know about the rest of Europe, but here in Germany people have openly talked about their salary with me in several occasions. Granted, it wasn’t any coworkers, it was always a friend or someone I knew.
It's not a digital wild-west open style though:
1. You have to authenticate using something which identifies you specifically as a citizen.
2. Another caveat is that people who gets looked up will be notified about that, with information about who it was who looked them up. (so it can't be used for direct covert spying)
That said, this system allows for a certain degree of transparency, and makes it easier for journalists, press, researchers etc to dig into issues such as social inequality.
I can see this one being taken to the EU Court of Justice by someone.
Norway will be subject to EFTA court, which is almost de-facto Court of Justice.
Granted, how someone might sue and escalate an case is a different thing altogether.
This is balancing between privacy and transparency of tax system.
I don’t think the EU privacy legislation applies to this kind of public functions.
Keeping the pay secret is kinda puzzling on traditional fields as the salary structure is very rigid on those due to strong unions. Doesn’t apply much in IT though where it is just minimum wage set by unions and you negotiate for (much) more.