One of the things we did to replace tubes at Trek was to cut a piece out of the damaged tube and drill some holes so a bungee cord could be used to put tension on the stump to be removed. Then a couple torches with "rosebud" tips to heat the joint until the brass melts. The bungee cord puts a uniform, straight tension on the stump and minimizes the risk of damaging the lug when the tube is extracted.

The problem with twisting the tube during removal is that this often destroys the lug.