The boxes chef/ubuntu-12.10 and chef/ubuntu-13.04 are available and working, however when installing packages 404 errors occur due to all packages being missing:
Err http://us.archive.ubuntu.com quantal-backports/restricted i386 Package 404 Not Found [IP: 91.189.91.15 80]
...
While I am not sure if this is deliberately done by ubuntu, the versions are end-of-life and the 13.10 and 14.04 are working as expected.