http://www.bolterandchainsword.com/index.php?showtopic=195378&st=125&start=125Long story short, Dan Abnett considers it canon that Ravens are loyalist 1kSons, Aaron Dembski-Bowden does not. This means that GW has not given any official line to the BL writers either.
It wouldn't be impossible though, Minotaurs have "chimeric" gene-seed and behave like loyalist Iron Warriors according to Imperial Armour 10.