Apparently CryptoWall does a dumb copy of the files before encrypting them and do not zero-out after deleting. If it still proceeds this way, that makes it fairly easy to do some recovery.
Hey, that's really useful/helpful info! I'll endorse TestDisk/PhotoRec as a mechanism for recovering deleted files, should be appropriate for most (though you might want a trusted tech savvy person to execute this recovery). The System Rescue CD includes these packages.