The manual states: "Eventually, the warp-drive engines of the four supercarriers reached critical meltdown. After twenty-eight years of warp travel, the huge ships emerged into real space near the edge of a habitable star system. Some 60,000 light years from the Earth, their engines destroyed and their life-support batteries nearly exhausted, the ships engaged their emergency protocols and plummeted towards the nearest habitable worlds in the system."
The Confederacy, Umojans and Morians were originally located in the same system. It is not stated if the system has one star or multiple stars, but that distinction is academic. However, the naming schemes of several planets in manual (Tyrador IX, Dylar IV) suggests that terrans have colonized multiple systems. I suspect that this is a mistake due to poor proofreading (since the author's ideas clearly changed over the course of development), and that the three power blocs are meant to be in separate systems.
BSG had the twelve colonies based in a multi-star system.