The update should be located here according to the Office Preview site and the mail I recieved from the Beta team and indeed all the other Office products and the now separate download for "Save as PDF / XPS" can be found here, but if you want the Office 2007 System TR you need to look here. Notice the following warning before installing
IMPORTANT: Please read the update documentation, referenced in the "To install this download" section on this page, BEFORE applying this Beta 2 Technical Refresh update. The documents list several steps that you must complete prior to installation to ensure a successful update. This is NOT a single click update.