Are there any in the vaults we don't know about? Given some of the drek they've put on albums over the years I'm inclined to think not, but I did read once about some songs that were written for VXI but not included on it. Hmmm...
If they've been unreleased all this time, would they be worth hearing? As you said, given the crap they've filled out their albums with now and then, I doubt if anything they've left unreleased would be worth the effort