This has been done a few times in Greece. But the gov't has installed special nets that are closed to stop the helicopters from either landing or taking off. I'm surprised all prisons in Europe - especially in France where crazy breakouts occur - don't have systems like this in place.
In Holland we had four/five heli escapes in the 90s, now it's very difficult to pull it off, but they tried it last year (about ten people) to free mocro boss Benaouf A., they all got arrested one guy was shot dead by police. In the 2000s there were several succesful helicopter escapes in Belgium.
