I think you will find that most glider sites have an ATZ which extends up to 2,000 ft agl but quite a few do winch launches to heights exceeding this - Syerston springs to mind with winching up to 3,000 ft - I certainly wouldn't want to get wrapped around any of those cables so steer well clear!. .. .I suspect that a lot of the problems are caused by everyone wanting to fly around at 2,000 ft in light aircraft, for some strange reason. Admittedly in the UK the cloud base sometimes forces one to do this but why not fly higher to avoid these airspace hazards?