Kenntnis der Deutschen Bahn von der Nichtumsetzbarkeit des Baus eines Verbindungsstollens im Filderaufstiegstunnel/Stuttgart 21

This question asks about the German national railway company's awareness regarding the impossibility of constructing a connecting tunnel for the Filder ascent tunnel as part of the Stuttgart 21 project. It seeks to understand what the railway knew and when, potentially impacting project feasibility and public trust.