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Ken: Mr. Wimmer, can you imagine headlines "Vladimir Putin has listened to cellphone of the German chancellor for ten years"?
Wimmer: That would lead to revolutionary situation in Germany.
Ken: And if they would say "China runs a flat spy operation in Germany"?
Wimmer: They are accused of that anyway.
Ken: But why nothing happened after NSA affair? At first they said "we don't do such thing", then "we do it a will do it further".
Wimmer: That's a question of national dignity.
Ken: Do we still have it?
Wimmer: You already answered that.
Ken: Did I?
Wimmer: By asking the question. If it happened anywhere else, we would definitely cut the contact. But the reality is, as you just described. Business as usual.
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Based on information from interviews like this, I think that nothing has happened, and no action was taken. US (correctly) assessed, that Germany can do nothing, and did what they wanted/needed/whatever. Germany can't do anything from it's position of weakness.
If Germany wants to change that, the steps necessary do not take into account the past, current or future US administration. Only German interests.