I don't think you can do it directly (as Ubuntu does not package the changelog info directly anymore, so this: http://superuser.com/questions/137818/easily-view-a-list-of-changes-of-upgraded-packages won't work anymore), but you can piece the information together yourself.
You can look at the log:
Show apt-get installed packages history via commandline?
This is the sample output from my machine:
Start-Date: 2013-10-29 20:29:59 Commandline: aptdaemon
role='role-commit-packages' sender=':1.89' Upgrade: upower:amd64
(0.9.22-1ubuntu1, 0.9.22-1ubuntu2), firefox-locale-en:amd64
(24.0+build1-0ubuntu1, 25.0+build3-0ubuntu0.13.10.1), firefox:amd64
(24.0+build1-0ubuntu1, 25.0+build3-0ubuntu0.13.10.1), polly:amd64
libupower-glib1:amd64 (0.9.22-1ubuntu1, 0.9.22-1ubuntu2) End-Date:
From there you can then look up the packages.
I searched on launchpad.net for "upower 0.9.22-1ubuntu1" and got the following page https://launchpad.net/ubuntu/+source/upower/0.9.22-1ubuntu1
Which then has the following info:
Cherry-pick two fixes from upstream:
- up-client: Really don't overwrite retval with prop values. Properties
and property notification via libupower-glib got broken in 0.9.22.
Incorrect values were being returned, meaning anything relying on these
might do the wrong thing, such as in LP: #1238663
- lib: Fix crasher calling _about_to_sleep_sync(). Crash fix. -- Iain Lane Mon, 14 Oct 2013 11:41:36 +0100
You can do that for any of the packages that interest you.