Thanks for the link to the source you used. 

Context of the document : "perspectives de revalorisation de la Senne à Bruxelles" 
During the afterwork there was a presentation of "Plan de Gestion Eau de 2016-2021" and focused on " Rainwater).

https://www.coordinationsenne.be/downloads/2017-06-27/2017-06-27_rapportFR.pdf

It was on the same period of the elaboration of the CRU 4 "avenue du Roi" and the designation of a study office (TED publication number
    2017/S 120-243891) 

A part of the study concern the hydrologic aspect, and explicitly refer to this path as a possible derivative of rainwater :  (final rapport) https://document.environnement.brussels/opac_css/elecfile/STUD_2019_HydroAvRoi (p23) and also BRAL mention this passage on this perspective : https://bral.brussels/sites/default/files/bijlagen/VORST_SUR_SENNEcompte_rendu.pdf 

Nobody name this path as it was the name, only on perspective of using it on that purpose.  (water from Preckher to the Senne). Finaly the project was not technicaly realistic.

On the ground aspect : I have said there is no sign on my first ground survey, i made a second one and found on the former entrance in Rue Preckher a sign that is inlaid between the roof of the tunnel and the metalic  wall that block it. The sign is realy on bad shape and only "(...) (pass(..) serv(...)e rés(...) à l'Une(r?g?) can be read (and some nl too). As there was a "centrale a gaz" there and the company was part of UNERG after being electrabel it's more than possible that this private way( that belong to Infrabel ) was only a service path and don't have name.


