I don't know exactly how LFL treats FFG material, but no reason FFG star systems can't be included in the appendix, and FFG folks have helped me catalog their contributions. The inaugural Atlas appendix included star systems from things that were "quasi-canonical" parts of the EU, such as old Polyhedron and Dragon articles for the WEG systems. Basically, the rule we went with then was "the planet exists even if the events might or might not have happened." Same philosophy works here. Yeah, sometimes you just sprinkle. And sometimes Dan and I used that for suggesting stories: there are a lot of GCW battlefields around Virgillia to suggest a long-running rebel conflict, CW battlegrounds around the "foundry of the Confederacy" near Metalorn, etc.