The Court of Justice delivered on 28 February 2019 its judgment in case C‑579/17 (BUAK Bauarbeiter-Urlaubs- u. Abfertigungskasse v Gradbeništvo Korana d.o.o.), which is about Brussels I bis:

“Article 1 of Regulation (EU) No 1215/2012 [….] must be interpreted as meaning that an action for payment of wage supplements in respect of annual leave pay brought by a body governed by public law against an employer, in connection with the posting of workers to a Member State where they do not have their habitual place of work, or in the context of the provision of labour in that Member State, or against an employer established outside of the territory of that Member State in connection with the employment of workers who have their habitual place of work in that Member State, falls within the scope of application of that regulation, in so far as the modalities for bringing such an action do not infringe the rules of general law and, in particular, do not exclude the possibility for the court ruling on the case to verify the merits of the information on which the establishment of that claim is based, which is a matter to be determined by the referring court”.

Source: here