At large the services you described were merged, or rather taken over, by their respective West Berlin counterparts. The 12,000 policemen in East Berlin were taken over by the newly established police for all of Berlin. The same is true for professional firefighters.

The mail and communication infrastructure of the Deutsche Post (GDR) was taken over by the Deutsche Bundespost (FRG) for the mail services and the Deutsche Bundestelekom for the telephone services, both of which were still state owned at that time. The Reichsbahn (GDR), i.e. the railroad company, was gradually merged with the Bundesbahn (FRG), also state owned.

Problematic was the size of these companies in the GDR. All of them were quite bloated and had far too many employees to work efficiently (Deutsche Post 229,000 employees Deutsche Reichsbahn 252,000. The number for the Bundesbahn was 249,000 in a country with at least 4 times as many inhabitants and much bigger railroad network). Downsizing had already begun before reunification with the monetary union in July 1990 and continued throughout the early 1990's.