Can't say I've ever done it myself (or even knew it was an option, to be honest), but I found some info about it on the website for a shipper I've used before here: https://www.a1autotransport.com/auto-transport-services-via-train-how-it-works/
Honestly one of the most disturbing things I've seen over a lifetime of watching sports. I actually said out loud "Oh my God, please be okay." So glad to hear he's doing much better.