Thanks for the information Richard, this is one trick that we weren't aware of.
We do however have one more question. Even with this very minor rolling process, just how much damage is done to the enamel insulation? (After all we did note you said oil filled transformers.) We also presume that this is only for low voltage applications. (Say below 5000 volts)
I've been gone, don't know where I went but I am back - jsut kidding. Generally the post rolling of the wire does not hurt the insulation because the elasticity of the film insulation is greter than the amount of deformation. Obviously if you "over do it" you could damage the insulation. Most of the post rolling is only making a couple of thousands changes in dimensions. I have not seen any hard data as to how much you can do but I think that it has is probably under 5% (one of the test elongates the wire 5% and then does a 180 bend and the insulation must not crack) plus the insulation must be properly adhered to the wire.
Again I don't know all of the details but I have seen it being done.
The wire was to be used in oil filled transformers. I do not know the limitation to the end product but this plant was making small distribution pole type transformers.