This lawsuit doesn't seem to stem from the GDPR, despite the article (mistakenly[1]) mentioning it. I don't even know if the regulatory bodies are enforcing the GDPR yet, much less in February this year, or even worse, 2015.

Here's a statement from the CPP, connected to the 2015 lawsuit. They mention Facebook being in breach of Belgian privacy laws from 1992.

https://www.privacycommission.be/sites/privacycommission/fil...

[1] - none of the other reporting I found on the subject(Guardian, Bloomberg, etc) mentions the GDPR. They also don't show the court order, which is frustrating.