I went. Expect it to be a real assessment. The day starts with them introducing their contract offer (5-year B2B contract, Ryanair style). After that, you will have a technical interview with two pilots and their questions range from Ops and Performance to Meteolorgy and Principles of Flight. Then you will be called to another room for the HR interview. If you pass this stage, you will have a sim screening on their Alsim performing a SID, STAR and approach, no emergencies, and psychometric tests. I can't tell you much more because I did not pass the first step. I was the only one with 200 hours...
They are looking for 787 and Embraer crews to be based in Warsaw and Budapest, 737 only in Warsaw.