If you mean http://changelogs.ubuntu.com, which aptitude (and probably update-manager) uses, then I guess it's an automated process.
Changelogs appear there alright, but usually after a while the package has available on repository. -- changelogs not available https://launchpad.net/bugs/61913 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
