The Kingdom of Belgium has tenuously united Dutch-speaking Flemish and French-speaking Walloons since 1830. Divisions between the two groups have meant that there has been no new government since the elections of 13 June 2010.
The Brussels metro previously broadcast French music (songs) at its 69 stations. Following complaints from dozens of passengers in April, the operator of the Brussels metro STIB has banned both French and Dutch music to avoid offending customers. Dutch music had actually not been broadcast because they were not popular (in music charts) anyway.
Consequently, most music broadcast by the stations have been in English. This provided an opportunity for the promotion of Lady Gaga's latest album.
Music from French and Dutch musicians is not technically banned, provided it is sung in English.
See reporting in Le Post (in French).
Report from Le Journal on Télé Bruxelles
Lady Gaga dans le métro de Bruxelles by Zoomin_France