JR, when selecting source files for batch rendering, it would be a nice addition to be able to select source files from Media Manager, and have PA record tagging information in MM for the newly renderd clips.
Yea, unfortunately, there is no Media Manager access in the Script API. That is certainly something you would request Sony to add on their Product Suggestions page. ;-)
Please add a scripting API for Media Manager. 3rd parties could use this to enhance Vegas/Media Manager workflows. For example, it would be very useful when using Production Assistant to batch render to multiple target formats to have MM as an available source. Then, PA could optionally create entries in MM that include tags from the source clips. This is but one of many ways 3rd parties could improve the workflow if MM api were available to them.