The spell Entrap Spirit lets you trap an incorporeal being or a haunt in a mirror for hours/level, Will save negates. But I can't find any evidence that haunts have save bonuses. Is there a generic rule that might apply?
I don't think that a haunt gets one, only incorporeal creatures do, because haunts don't have saves.
The text is clear about haunts not getting will saves vs channeled energy. I think they should have written that as haunts just don't get saves period but they didn't really anticipate a lot of spells that could target a haunt directly.