TSMADump can easily get all the forwards for a specific account. Here is an example of the syntax...
TSMADump USERFORWARD http://mail.test.com admin foobar fred
This command would list all the forwards (if any) for the user "fred". "Admin" is the host admin username and "foobar" is the host admin password.
You can download TSMADump here...
http://josh.com/tsma/TSMADump/index.htm
...and it includes several examples of how to dump user forwards, including the batchfile FINDYHOO.BAT that will list all the users that have forwarding to Yahoo set up.
Let me know if you have questions.
-josh