I'd ask the German federal police about this. After all, counter-intelligence against foreign state agencies is their bread and butter... (/snark)

Not even military. Germany has foreign and domestic intelligence agencies - the Bundesnachrichtendienst (BND) and the Bundesamt für Verfassungsschutz (BfV), respectively. They don't need the po-po's helicopter to check for antennae. They already know or can reasonably guess what intercept equipment is on-site at the consulate (and other sites).

If this stunt's goals were any more transparent, birds would be smashing into them with the frequency of that Hot Butter song.