Deke, take a peek at this Nuke script and let me know if that's what you're looking for. The script is really just showing how mutual cutouts behave with the various methods of blackening the channels and may be misrepresenting the quality of the stock DeepMerge:holdout mode since the input deeps are dcx encoded.
The only thing missing from the script are the deep exrs with bunny & dragon rendered together, I'll have to dig those up and put them in the download folder.
I'm also making a simpler example script that has all the dcx nuke plugins represented and I'll post that when it's ready.