This is not any kind of joke. There actually IS a bus in Brussel, which goes to the "Wiener". It is on the same level as the German words "Kunde" and "Kurve" which mean "Customer" and "Road Turn" and those words are very similiar to the Czech words "Kunda" and "Kurva" which mean "Cunt" and "Bitch".
So in this logic it absolutely OK, that there exists bus which goes to Wiener. :oD