If I make something in Flash that has action scipt, and import into AferEffects with Actionscript translated into AE expressions and vice versa?
No. AE does not interpret the Flash file, it will simply treat it like a footage item and that means that scripts inside the Flash file will not be evaluated, only linear animation. For more info on supported features refer to the help.
I though XFL files were translateable in code to. hm oh well. What about from AE to Flash will AE expressions get Action scripted?