Is there any way to access the Photo Stream outside of Photos.app in El Capitan
So, I've answered this for myself: iCloud Photo Library photos are buried in subfolders of "~/Pictures/*.photoslibrary/Masters" on El Capitan!

Using a savedSearch, the same approach as was popular under Yosemite and earlier, we can create a Finder folder that lists, chronologically, your Photo Stream. The XML version is here (you may have to modify some paths), or you can download my pre-compiled version instead:



Ta-da!