Re: Other angles
Perhaps as the state hosting both the EU & NATO headquarters there are a lot of 3rd party countries doing sneaky beaky stuff that we both are quite keen to keep tabs on.
I have no doubt that there's an element of this. Lower level NATO <Classified> documents will be in the Kremlin before they've been read by everyone on the official circulation list. It's blatantly obvious that you'd want to be keeping an eye on who is talking to who, or sharing what and where - and if Belgian spooks aren't doing it (or aren't sharing), then you do it yourself.