Answer ... No explicit provisions in the German Arbitration Act address the consolidation of separate arbitration proceedings. Consolidation is nevertheless considered to be permissible, but it requires the unanimous consent of all parties in all proceedings that are to be consolidated. Under no circumstances can separate arbitrations be consolidated against the will of one of the participating parties.
The arbitration rules of the German Arbitration Institution explicitly contemplate the consolidation of arbitration proceedings, but likewise require the consent of all parties involved.
Answer ... The German Arbitration Act does not address the joinder of additional parties. Failing an explicit prohibition in this respect, such a joinder is generally possible even once the proceedings have already commenced. However, it requires the explicit approval of all parties involved, including the tribunal. Only under this condition of mutual agreement can a new party effectively join (ongoing) arbitration proceedings.
Answer ... Assignees of claims for which an arbitration agreement had been made by the assignor are likewise bound by the arbitration agreement. The same is generally true of legal successors and even insolvency administrators.
Beyond this, German law is extremely cautious about extending the effect of an arbitration agreement to third parties which are not signatories to the arbitration agreement. The ‘group of companies’ doctrine and similar concepts are widely rejected, both in legal commentary and in practice.