10.5.2 places a Time Machine menuextra in the menu bar for all users. 
We’re not encouraging the use of Time Machine in our organization. I’ve removed it from the default dock, and am managing the preference to prevent Time Machine from asking if you want to use each new external disk for backups. Users can still use Time Machine, we’re just de-emphasizing it. Therefore, I want to remove the Time Machine menu extra from the menu bar by default.
If you import the Preference Manifests in /System/Library/CoreServices/ManagedClient.app, you gain the ability to easily manage MenuExtras. But the Time Machine menu extra has not yet been added to the list of menu extras. No matter – you can edit it like so:

Just select Edit… from the popup menu and enter TimeMachine.menu instead of one of the pre-populated choices. You’ll see the little badge warning you that your entry does not match the manifest. That’s OK, it will still work. Setting the value to “false” will cause the TimeMachine menu to be removed from the menu bar at the next login.
I’m managing it once, so it’s off by default, but users can turn it back on if they want.