I haven't got GalCiv 2, but Frank Klepacki, the original Red alert composer is supposed to have done RA3 music (Hell March 3, at least
), but it's not uncommon for two different musics to have similar passages, for example, one game i played on SNES had music that had exactly the same part as a TV-series tune. The shows in question was made by finnish for finnish, so i doubt the american composer had heard that.
BTW, there are indeed sound banks, that can be used in any game, TV-series or movie, but in my understanding they are only sound effects, i can't count how many times i've heard the exactly same "rusty door opening" sound, or the exactly same dog whine, or the exactly same angry cat, or...