Someone at this forum ,explains hot to peek into an update image from a standalone device:
http://www.oesf.org/forums/index.php?showtopic=16826

so... if the base system is the same... it should be possible to "mount" this image and chroot into it...

update:
at a latter post on that forum, they mention:
"...Angstrom *will* run zomtom without any patching..."

and I believe that Angstrom is beying ported to the 770/800, right?