It's part of the map seed. So, if you play with the same AI type, same map seed, same map size, same starting position, etc, you'll always get the same fabricators, etc. But it isn't connected to anything you do in a meaningful way; i.e. if you pick vampires that doesn't have any bearing on the core demon hand fabricators, etc.
EDIT: And, rubikscube, actually what you choose as a starting ship does have more of an effect on the ARS, even. Partly because it affects the starting map seed (as with the fabricators), but also because it changes the pool from which the ARSes can pick new ships from. ARSes only ever grant you ships that no one on your team has unlocked yet, so depending on what you unlock that can affect the random seeding within what's remaining to a certain degree. Fabricators aren't affected in quite the same way.
Think of it like Chaos Theory: a butterfly flaps its wings in China (you unlock ship X) and the weather is different in Seattle (different fabricators are seeded). It's all very indirect and not something you'll be able to predict. If you make the same choices you'll get the same result as last time on the same map seed, but that's about as predictable as you can make it.
