*digs up copy of X-Wing Strategy Guide*
What you have to realize is that Ackbar was feeding data to the Rebels before he was rescued (just like Madine did in DF). Ackbar wasn't "rescued" (as a prisoner) so much as he was "extracted" (as an Intell Agent).
The rescue of Ackbar is in the Original X-Wing game, historical combat, Y-wing mission 6: Interception and Capture.
I haven't played X-Wing in years, so the exact details are a little rusty. Recommend you find someone who's more familiar with the specifics than I am.
Tactical Summary (paraphrasing now)
Five Imperial shuttles (Epsilon group) with TIE escorts are en route to the frigate Vehemence. One of them is carrying Ackbar.
The 3 Y-wings attack the TIEs first (the TIEs are flying in several groups of three). After the TIEs are mostly dead, the lead Y-wing switches to torpedoes and starts doleing out one per shuttle (to knock down shields and confuse control systems).
(By now, the other two Y-wings are duelling TIE reinforcements from the Vehemence.)
After all five shuttles have taken one torp, the Y-wing switches to ion cannon and start doing recon flybys. Y-wing sensors aren't all that great, so the Y-wing has to do a few "near-misses" as it zig-zags through the formation.
Shuttle Epsilon 5 is the one carrying Ackbar, and the Y-wing disables it with three or four ion blasts. As soon as Epsilon 5 is IDed, the Rebel shuttle Hasti drops out of hyperspace to dock.
After a few moments, TIE group Gamma leaves the Vehemence heading for Hasti. At this point, the Y-wings turn it into a simple guard mission while the Hasti docks with Epsilon 5, picks up Ackbar, and hypers out, followed by the Y-wings.
"Do fish-people eat fish, or would that be like humans eating monkeys?"
"Humans do eat monkeys. In fact humans eat other humans. . . Y'know, as a species, we are really quite unpleasant."