Re: Welded Rail and Free Trade..........the tales of the rails.....
Here is a link describing the product. You may have to click the "See the Product Details" button.
https://www.nssmc.com/en/product/use/railway/
And for the techies among you we have this. There is a pdf at the site too.
http://www.nssmc.com/en/product/construction/list-construction/37.html
And to the question: UP was the first, and since that was in 2015, probably the only one at this time unless they are buying it from UP.
https://www.up.com/aboutup/community/inside_track/long-rail-3-27-2015.htm