Posted by Andrew.
Google Launched Google Buzz some days ago. Unfortunately, it isn't added to Google Apps account. There's no definite word as to when, just "within a few months". :-(
Google enterprise blog said:
Within a few months, we also plan to make Google Buzz available to businesses and schools using Google Apps, with added features for sharing within your organization.
There is a discussion in Google help forum:
Answer: can I use buzz from my email@example.com mail? (which has business gmail service set up)
A reply from Google Employee:
Just letting you know that I've passed all of your feedback on to our product team.
Unfortunately, turning on a new feature like this for an Apps account is a little different from turning it on for a Gmail account.
When enabling this in Apps, we need to provide other administrative controls, like allowing it to be turned on/off at the domain level, security restrictions (who you can and can't buzz to) and the like.
This will definitely be available some time soon, and we appreciate your patience in the meantime.