That code is just a prototype, the seed around which the rest of the game nucleated. There is a big thick layer of behavior trees, hierarchal state machines and lots of whatever layered on top, including a visual behavior tree programming language called "SimAntics" and an editing tool called "Edith", which is described and demonstrated here (starting at 11:20):
Here's another demo of some tools for making and managing user created content for The Sims, and SimSlices's amazing version of SimCity embedded in The Sims!
To clarify: SimAntics, the behavior tree visual programming language actually existed before Will wrote the "Soul of the Sims".
SimAntics was used in SimCopter for controlling the little Sims with simpler souls who walked around the city, for dispatching the police, firemen and medics who picked up injured Sims and brought them back to the helicopter, as well for implementing the notorious gay easter-egg with a bug that caused hundreds of shirtless "himbos" in fluorescent fog-piercing speedos (using the same special render as runway lights) to swarm all over the city hugging and kissing on Friday the 13th!
