Visit the following page to subscribe to the new Trac mailing list:
http://lists.automattic.com/mailman/listinfo/wpmu-trac
You should only subscribe if you want to receive notifications of all Trac activity. If you're only interested in a single bug you should add your email address to the CC list of that bug.
Take a look through the archive first before you decide to subscribe:
http://comox.textdrive.com/pipermail/wpmu-trac/
