After reading the hdid man (via man hdid) page, I realized that we could mount .DMG images via HTTP under Terminal.app. And even cooler, the segmented images work too. Just reference the http-based DMG via this command:
% hdid http://server.company.com/Images/stuff.dmg
[robg adds: I haven't tested this one. The man page has a lot of good info; search on Mounting Images to jump to the section on http-based images.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=2005050606123892