Quantal has now appeared in the old-releases.ubuntu.com mirror! Happy Days :)
[obsolete answer follows]
This week the main ubuntu mirror seemed to drop 12.10/quantal repository package pool altogether. Old-releases still has not picked it up, and like everyone else here, I'm struggling to find any information on future plans to do so (or not).
In the meantime, we found a repository that still contains some packages:
Currently we can only confirm the quantal and quantal-updates distributions, with main, and universe sections for each, restricted and multiverse are there but fairly incomplete.
While this does not answer the question I thought I'd document my resolution while there is still some life in at least one repository:
Mirror the repo locally
Here's an example of doing it with debmirror - I'm behind a corporate firewall that only allows http/s (no rsync or ftp), and requires authentication so I've accounted for those restrictions in my options. You'll need about 87GB for binary packages for i386 and amd64 architectures combined (from memory, sync still in progress here). I would triple that if you need source packages too:
sudo apt-get install debmirror
sudo debmirror --progress --verbose --host=ftp.belnet.be/ubuntu.com/ubuntu/ \
--method=http --proxy=http://user:pass@proxy:port --dist=quantal,quantal-updates \
--section=main,universe --arch=i386,amd64 --nosource /path/to/local/mirror/
Hope that helps -