after Tasha's execution, their fate will rest in the hands of a Volskiar who isn't depicted in Treklit as a generous kind of person, especially if he's felt himself cheated.
I'm sticking with my suspicion that Charvanek could have somehow arranged for their release or escape. She's got connections herself. She couldn't do anything for Tasha, but could help the other survivors. And since she fought alongside them, she'd have every reason to.
As for Picard's skepticism about survivors? Maybe he just didn't know about them.