In Battlestar Galactica (2004) it is eventually revealed that the
"Final Five" cylons
are, in fact, characters in the fleet.
However, it seems like an amazing stroke of luck that all of these characters were spared when the colonies were attacked, especially considering they didn't even know they were cylons so they couldn't have conspired with the others to get out of the way.
Is there evidence that the cylons somehow knew to wait until they were all out of the way (e.g. in space) before launching their attack on the 12 planets?