As argued in the response you link, it depends on your definition of "recover" (i.e. do you still trust a binary after it was potentially changed by anybody on the system, which may be "I guess I'm ok" for your private desktop machine but much much less so on a multi-user company system).
Looking at my box, /bin has a manageable number of files that aren't 0755 or symlinks:
ls -l /bin/ | grep -v '^-rwxr-xr-x' | grep -v '^l' | wc -l
35
and that's mostly because they're setgid or setuid. So in principle, you could chmod 0755 /bin/* and manually fix the permissions on those 30, 40 binaries, if you still have root access. (su and sudo won't work until their proper permissions are restored.)
But for practical purposes, that still means you need a "clean" machine somewhere for comparison purposes, but you don't need to mount its drive.
(Come to think of it, I don't think wrong permissions on the binaries should stop the package manager from working, so you could conceivably try reinstalling every package that has something in /bin, but probably most everything has a dependency on something in /bin, so you might end up removing and reinstalling all packages.)
