Here is what I have on this formation.
On 23 April 1945, just as the Russians were at the very gates of the Berlin, GenLt Hellmuth Reymann was relieved of his post as Commander of Fortress Berlin and appointed commander of Army Detachment Spree in the Potsdam area. This formation consisted of one under strength division (Division Jahn, a unit still in process of being formed out of Labor Service components). This force was committed to action along a 40 kilometer front facing south on either side of Berlin. His removal from Berlin was obviously ordered at the insistance of Goebbels whose initially favorable attitude toward Reymann had radically altered. When Generaloberst Heinrici, to whom Berlin was at this time subordinate, learned of the change, he ordered Reymann to remain at his post because it seemed to him foolhardy to change commanders at a time when the danger was most acute. He was not able to make his orders prevail, however, and Reymann took over command of "Armeeabteilung Spree" and, with part of this force, he was driven back to Potsdam and surrounded. His force, numbering some 20,000 men was eventually evacuated through a narrow corridor which was held open by the 12th Army.