I'd be curious to know. I'm basing that theory from what Dav said during the BGS livestream some time ago. I thought i recalled them popping up in civil war CZ's as well, but I could be remembering incorrectly. Since he made the comment, whenever I've come across them it's all been in a War scenario.I've seen Civil Wars with capships. I'll keep my eye out next time and get screenshots.
I recall (but don't take my word on it) that there were other "factors" that influenced whether Captial ships would appear (in High CZs) relating to underlying factors (e.g wealth, overall influence etc) but definitely take that with a grain of salt.
Does anyone know if Walt updates the OP anymore? Is he even still around? I haven't seen him in a while.