Thanks for the feedback again -- no dice though. I've found several sources that correlate with what you're saying, some including charts to indicate which browsers will do what with the favicon. Unfortunately, these charts appear to be outdated. I can't, for the life of me, get any browser on either system to use the favicon for the desktop shortcut. (Works in the browser's links bar and favorites menu.)
If there's some subtlety I may be missing, hopefully someone can point it out.
My employer is very picky and detail-oriented. I've even gone so far as to creating an inline, data-uri shortcut "file" on the fly. In the scenarios I've attempted so far, I can get the shortcut file to drag-drop successfully (on windows), but designated icon still fails to show. (Maybe the image can be embedded in the shortcut file?)