bxl-forever
They have been mapped for years.

De Brouckère:
https://www.openstreetmap.org/way/685995316
https://www.openstreetmap.org/way/685993866

Bourse/Beurs:
https://www.openstreetmap.org/way/669535985
https://www.openstreetmap.org/way/685993866
https://www.openstreetmap.org/way/669166052
https://www.openstreetmap.org/way/669533607

