If I misunderstood your question, I'm sorry. To get an alpha out of AE, you need to render in a format that preserves alpha. (Quicktime with the PNG codec, for example.)
If you need to turn a layer that's white with a dark shadow on it, the Unmult plugin (free) can do it for you.
Shadow passes and AO passes have no Alpha due to how they are generated internally and what data they actualyl represent - not in any 3D program I know and not in Cinema 4D specifically. You have to manually unmultiply them if you need that functionality.
Sorry but maybe i didn´t explain well, excuse me for my english!!!
I wish to have the shadow and the AO passes with alpha channel information included via cineware.
I think this may be an issue with cinema since i´ve been trying to do this same way as in Maya usebackground shader does.
Ok shadow cacther plugin do it, but wath about cineware????
I want to do the final render in AE but need alpha shadow, AO...
Thanks for the anwers!!!!
Unmult is the way....