The Fall of Shadowbrink shows us that the daemons cannot draw any kind of sustenance from the tyranids. Bugs simply don't have any kind of emotion or soul, at least not in any measure the daemons are able to draw power from.
If Ka'bandha really was behind this, it was an act of desperation and nothing more.
I know there's nothing mentioned about them here, but I also wouldn't rule out some necron involvement. The Silent King admitted to a healthy respect and even admiration for Sanguinius, so it isn't entirely impossible that the necrons are still pulling strings where they can.
Not an encounter Ive heard of, elaborate? Devastation of Baal will surely cast more light on the KDK involvement and plans.