When the #BND headquarters moved to Berlin in 2019, the department for signals intelligence with its 1000 employees stayed at the old BND-compound in Pullach in Bavaria, which is close to the famous satellite station Bad Aibling https://www.electrospaces.net/2014/05/pictures-from-inside-german.html
The Russian agent, called Carsten L., is said to be an officer of the German armed forces, who served as head of a unit (Referatsleiter) in the BND's department for signals intelligence (Abteilung Technische Aufklärung)