Following closely on the heels of the Gamers with Jobs interview, HomeLan Fed has released their interview with Dallas Dickinson about Core Combat. Here's one question and its answer:
HomeLAN - Why was the decision made to concentrate on underground combat for the first expansion?
Dallas Dickinson - We wanted to create a new combat environment for the game. PS has fantastic outdoor battles and some crazy close quarters fighting (in bases and towers), but it doesn't have a good analog to the urban combat that is so popular in other FPS games. Creating these underground cities allows us to do that, while keeping air support from absolutely ruling the game. The Liberator is pretty powerful still, but it will always be in range.