Were the C survivors that Yar traded herself for repatriated to the Federation at some point?
I'd like to think so.
My personal theory is that during, or near, the events of Vulcan's Heart
, Charvanek arranged to have the Ent-C survivors returned to the Federation. She seemed like a fairly reasonable person. Of course she couldn't do anything for Tasha, who was already the property of that Romulan general, but I'd like to think she could help the other survivors.