Drivers for these cards are now available in a separate branch called legacy series. Unfortunately these legacy drivers (version 12.6) have not been updated to work with Ubuntu 12.10. Ubuntu 12.10 comes with xorg 1.13 while these drivers have support for older xorg 1.12.
So if you want to install these drivers in Ubuntu 12.10, you have to downgrade to xorg 1.12. A PPA has been provided by Tomasz Makarewicz that includes all the required packages you need to downgrade plus a fglrx-legacy package.
To install these packages, run the following commands:
sudo add-apt-repository ppa:makson96/fglrx
sudo apt-get update
sudo apt-get upgrade
sudo apt-get install fglrx-legacy
Do note that these packages are not officially supported by Ubuntu, so use them at your own risk. If something goes wrong, you can purge the packages by running following commands:
sudo apt-get install ppa-purge
sudo ppa-purge ppa:makson96/fglrx