Some corrections
Richard Cox from Spamhaus came to Vienna to attend http://www.spamsymposium.eu/ . The meeting with me as an employee from nic.at there was pure coincidence.
There was no constructive dialogue as I am not involved in the .at part of nic.at and thus could not act as a representative of nic.at, and all Richard said was "do as I say or else". That's not a dialogue: that's blackmail.
The block is symbolic *now*. It was a /24 when introduced. That isn't documented on the spamhaus page, either.
Summary: don't just accept the spamhaus proclamations as truth. They often aren't.