– the arbitral tribunal was held competent to decide on costs even if it denied jurisdiction on the merits;
– the arbitral tribunal’s decision declining jurisdiction was qualified as an arbitral award;
– and that an action to set aside such an arbitral award is generally admissible.

Значит ли это, что существуют три возможных решения Федерального верховного суда Германии?

Ниже на двух страницах рассматриваются все три варианта решения и делается такой вывод:

No difference in treatment is made between positive and negative jurisdictional decisions by arbitral tribunals for the purposes of challenging these awards. It may therefore be assumed that an arbitral award denying that the tribunal has jurisdiction is not treated differently from an award confirming jurisdiction as regards its preclusive effect under English arbitration law. Consequently, an award denying jurisdiction is also attributed cause of action and issue estoppel, and hence precludes any court decision to the contrary.

Спасибо.

Если так, то можно сказать три подходящих (для нас) правовых сценария развития событий

Типа: хоть так, хоть эдак, в любом случае, все будет хорошо. имхо