I played a Void Crusade Rescue Mission yesterday, where you have to find three groups of Guardsmen and bring them to an extraction point.
I cleared the whole map of enemies and brought two groups to the EP, then went back to the third group. They didn't move. Didn't follow me or anything.
The mission didn't fail though, so I could only abandon it. But it somehow failed the whole Void Crusade, even though I still had 5 Life Counts left?!