For those who don't know, there's a Union Pacific M-10000 on the DLS, but it was released back in 2010. (anyone is free to share their Trainz M-10000 pics here)
Yes, the M-10000 is still available and it can be downloaded from the DLS via Content Manager. Last time I looked, its name was M10K. If you look for Name = M10K and Author = whitepass, you should be able to find it.