Not retrieving schema list from source when migrating from MSSQL to MySQL using Workbench
In case someone else comes across this same issue, and you don't have access to the "sa" user, I thought I'd post how to resolve the issue.
The underlying problem is user permissions. Although you can login to the database fine there is a specific permission that needs to be set in order for it to work with MySQL Workbench. The permission you need is "View Any Definition" which is found under the users "Securables" tab.
There is a good short video explaining it all here http://mysqlworkbench.org/2013/08/video-tutorial-setup-a-restricted-sql-server-account-for-migrations-with-mysql-workbench/ and the specific part is located at 2:17.
If the database is on a shared host - as was the one I needed to access - I would recommend simply emailing the host (preferably via your clients main contact) and they will hopefully do it for you. The host in my case switched it on for 1 day as there must be some other potential security risks at their end having it turned on.
Hope this helps someone else out there.
Make sure you're connecting to MS SQL as user "sa". Non-admin users may lack rights that are necessary to extract schemas...