I think this mod is causing aliens to spawn even when the setting is set to none.

I ran into this today and after peeking at the source code, it looks like the culprit is the line:

to.config.enemy_bases_per_region = 2

(line 71, https://github.com/SirRichie/TrainOutpost/blob/master/config.lua)

I changed this to:

to.config.enemy_bases_per_region = 0

and it looks like it's solved the issue. I didn't read deep enough to know if this has any deeper implications, but my guess is it's setting a minimum number of bases that have to exist per region.

I'll try this out when i get home.