Joern,
I agree with you that what you describe is a likely outcome. I don't think, particularly in crossing (as opposed to opposite) traffic, that the chances of a collision are very high, particularly if both aircraft manoeuvre.
But "rather low", as you put it, is not a level of probability I'd be comfortable with if it describes mid-air collisions. I'd prefer "extremely remote".
But we know that at Ueberlingen they did collide, and what makes my hypothetical setup sufficiently different from Ueberlingen that everyone seems to be confident it would not be a problem?
Yes, a lot of factors have to come together, such as land-communications failure, ground based collision warning system failure, high ATC workload, ...
But it does happen in real life. And who can put a number on its probability?
Or even give a sound argument why it is low enough to discount in the face of an actual occurrence?
Bernd