Hi Ed
Yes. This is exactly this reason. The heavy batteries was to the defend the IG Farben ? At the end of january 1945 Ig Farben was defended by 156 heavy guns grouped in 24 batteries. Germans had plans development of defense. The date end this development it was 31.03.1945. At this time should be around IG Farben 198 heavy guns.
More details of course in book
Janusz