It seems my memory wasn't quite as reliable as I thought. It should read 170°C, not 200°C. Foot in mouth!
And there
are some exotic alloys used too. In addition is seems they do use this for new construction too.
The article below provides a good overview.
http://tdworld.com/ar/power_transmission_line_conductor/index.htm [This message has been edited by C-H (edited 02-29-2004).]