I hope this helps someone, I run into this question several times and found no useful answer.
Tip to Get Loco You Want
I had an issue, bought license for DM3 and teleported literally to every station on the map and DM3 was nowhere to find. I revisited those stations, but the same locos were there, they did not respawn (I heard they respawn after few hours of not using it), so I stuck in a world with DM3 for a while.
And I found a fix. DM3 is known to spawn at least in Harbor or Steel Mill, so I chose Harbor. I visited Harbor’s loco house, where there were always 4 locos. I used my remote, to remove all 4 locos for 0$ and teleported few hundred meters away (over water to the other side of bay) and then back (took like 10-15 seconds) and new locos were spawned on places, where I removed them. It took like 5 tries, but DM3 finally spawned for me.
So universal tip – if you don’t see any loco you want, just remove it with remote, get a bit far and return for a new RNG spawn.