Actually, you can set your signature on the Exchange server via OWA. This signature is stored in your mailbox (similar to out of office messages), although it is not utilized by the Outlook client when accessing locally. As di mentioned, Outlook utilizes the local signature files, so it's rather hard to keep these synchronized, if at all.
In other words, it is not worth the time and effort spent on a solution that will likely fail quite a bit. However, just some thoughts on the subject.
- BlackBerry stores the signatures in plain text in the database in the UserConfig table under AutoSignature.
- Outlook stores the signatures in multiple formats (including plain text, in most cases) on the users' machines in %appdata%\Microsoft\Signatures\.
- OWA stores the signatures in the user's mailbox in a hidden folder (although I'll have to look to find it).
So to tackle this issue best, I think having a discovery process running as part of a login script to capture a user's signature from the local machine and comparing it's modified date to that of the hidden folder in their Exchange mailbox then updating the Exchange mailbox signature, if older. From there, you can capture that data and use a SQL injection into the BlackBerry management database with the signature.
...then again, you run the potential of corruption of both the user's mailbox and BlackBerry database, so maybe none of this is such a great idea...