Hello, I also had the problem with the trains not being available. I was probably working on the problem for 10 to 20 hours, but the problem has gone away since last Wednesday (June 19th). All trains spawn correctly again. I don't know what it is, maybe it's because I downloaded ScriptHook from Nexus Mods (https://www.nexusmods.com/reddeadredemption2/mods/1472) or maybe it's the new Rampage update, but it works for me again and I use lots of other mods. However, Railroad Engineer again led to train spawning problems for me.
I hope I can help you all with this.