It doesn’t. If you didn’t get it for all your systems, you can avoid certain bugs if you download (and install it) from After Effects for Macintosh or After Effects for Windows.
Premiere seems to have updated automatically. For more info on the recent update releases, see After Effects CS5.5 (10.5.1) update: fix for text entry bug and serial number problem and Adobe Premiere Pro CS5.5 (5.5.2) update: Maximus functionality and bug fixes.