I had been hoping that a utility would be made available for restoring from OneCare backups, but nothing has been announced, so that might not happen.
You can open OneCare backups with an archive program such as WinZip and manually extract files from the backup .zip files. If a backup split any larger files, you'd need to manually rejoin the split files after extraction.
This utility is free:
http://www.freebyte.com/hjsplit/
-steve
Microsoft MVP Windows Live / Windows Live OneCare, Live Mesh, & MS Security Essentials Forums Moderator