I came across a website where a guy did the same thing with some old Kodak lens. His website had a few more details about how he did it. Sorry I can't find it again today.
I assume it wouldn't be that hard to mount a EF adapter to anything you wanted too. Could always email the guy and ask.
I also think it was just positioned there, not attached. You can easily make a macro lens from your standard focal length lens just by positioning it towards your senser with the opposite side (i.e. reversing the lens).
He linked to the source, and its on a platform that by default allows sharing of content.
Plus with all the recent releases there was a flood of images and diagrams in the forum though i didnt notice you asking if they had permission, how's that?