I think they are referring to the following:
www.iasplus.com/en-gb/standards/ifric/ifric12
"Service con­ces­sion ar­range­ments defined

A service con­ces­sion ar­range­ment is an ar­range­ment whereby a gov­ern­ment or other public sector body con­tracts with a private op­er­ator to develop (or upgrade), operate and main­tain the grantor's in­fra­struc­ture assets such as roads, bridges, tunnels, air­ports, energy dis­tri­bu­tion net­works, prisons or hos­pit­als. The grantor con­trols or reg­u­lates what ser­vices the op­er­ator must provide using the assets, to whom, and at what price, and also con­trols any sig­ni­fic­ant re­sid­ual in­terest in the assets at the end of the term of the ar­range­ment."

Dutch term (edited): solidaire medeconcessieovereenkomst (BE)

- rather than a fully-fledged (building) lease, such as a precair opstalrecht (short-term right to instal a temporary structure at the dock - terminable 'at will' or 'at (short) notice').

I'm unsure translitierating into Belgian French - my usual tactic - works here: contrat de concession solidaire.

Property = land & buildings.