How can I add a PPA from a previous release?

You should choose Modify in Software & Updates > Other software from raring to quantal distribution.

After you add the repository, you can try to change the distribution manually:

$ cat /etc/apt/sources.list.d/eudoxos-vim-breakindent-<version>.list 
deb http://ppa.launchpad.net/eudoxos/vim-breakindent/ubuntu <version> main
deb-src http://ppa.launchpad.net/eudoxos/vim-breakindent/ubuntu <version> main

So just replace <version> on those entries with quantal, and do sudo apt-get update. It is not guaranteed it will work, but if it doesn't you can revert the canges or remove the PPA.

To avoid manual change of the sources list you can use the following command to add the repository for a specific Ubuntu version:

sudo add-apt-repository "deb http://ppa.launchpad.net/eudoxos/vim-breakindent/ubuntu <needed_version_here> main"

To remove the added repo:

sudo add-apt-repository -r "deb http://ppa.launchpad.net/eudoxos/vim-breakindent/ubuntu <needed_version_here> main"