I saw a program on the History Channel a while back called "Boneyards". They covered how different things are scrapped out and how the scrap is used to make some new product. I'm pretty sure the one about trains said there was a place, I can't remember exactly where, but thought it was Chicago or New York that recycles railroad rails into T posts.

It was a good program and would explain why U.S. T posts would be vastly superior.

Did a quick Google search and came up with this. I don't recall this being the place mentioned in the program but looks like the same sort of process using old rail.

http://www.cmcsteelar.com/difference/index.aspx

http://www.cmcsteelar.com/products/posts.aspx