Discussions on the topic appear mute. I only find one article that seems to touch on it but it requires a subscription [1]. As at October 2023, Fitch expected no spectrum auction in 2025 [2].
I also couldn’t find the link to the internal letter on BNetZa website.
I think there aren’t enough rules at the moment to guarantee sale of frequencies to the likes of 1&1 at favorable terms. But that’s one of the agendas of BNetZa Advisory Board meeting scheduled to be held at the end of September [3].
So far, information on its agreement with Vodafone only relates to national roaming. But they said they are still discussing the agreement, so maybe they would announce it in the full report.
I think even if there would be an extension, BNetZa will come up with mechanisms to please the likes of the Federal Cartel Office [4], the Monopolis Commission [5] and politicians [6] who have been in favor of the fourth MNO. That will possibly be favorable sale terms for frequencies.