Part of them turned up in the new Codex: Blood Angels;
So depending on various factors, we've now got a T'au colony setting up next to the Blood Angels...Bloody Retribution
Hurled across the void by an empyric convulsion, a T’au colonisation fleet begins claiming worlds within the Red Scar. Their efforts are brought to a sudden, violent halt by strike forces of Blood Angels, Flesh Tearers and the Angels Sanguine. The planets of D’sandri and Gendal’s Reach are swiftly reclaimed, and the war spills into the Sevensuns System.