I've still only seen the Rebels win ONCE on Sabotage on Adminstrator's Palace, just because bomb B is supremely fucked for the Rebels to take since it's so close to the Imperial spawn (not to mention Partner spawning) along with being super defensible. It's actually kind of absurd, I've played over 25 games on that map and it's always just a total blowout.
I've only done the other ones a few times, but I think I've seen them all go both ways but generally leaning towards Imperials. Even if the Rebels still have 3-4 heroes alive in the Extraction Zone it's still fairly easy to beat them if the Imperial heroes are solid and can take out the Rebel heroes. I get the dynamic they're going for with the heroes but I don't think it quite works out. Might be better if heroes are constantly spawning on both sides or something, either way it goes it's usually a blowout in my experience.