I don't know how far along you've gotten with this, but I located a pretty large DEM I made before it was trimmed down to suit my needs. It contains the CSX Kingsport Subdivision (former CRR mainline) from Elkhorn City, KY to Kingsport, TN, NS Appalachia District (former SOU) from Appalachia, VA to Frisco Yard, TN, the Western part of the NS Clinch Valley District (former N&W) from St. Paul, VA to Norton, VA, NS St. Charles Branch (former SOU) from Appalachia, VA to St. Charles, VA, NS Clinch Valley Extension (former IRR) from Tacoma, VA to Andover, VA, and the CSX Cumberland Valley Subdivision (former L&N) from Big Stone Gap, VA to Hagans, VA. These all include miles of branchlines servicing dozens of tipples. Tunnels of various lengths are everywhere, including the
Natural Tunnel which if you replicated in Trainz would make you a superstar in my book, and trestles, including the moderately famous
Copper Creek viaduct, are even more common. There is no way you'd ever be able to build up this entire DEM in any reasonable time, but if you are interested you can trim it down to the parts you want.