This can be determined by the value in the PRCATEGORY column in the PRDOCUMENT table.
- If the project was last updated by the new XML driver, the PRCATEGORY = 100.
- If the project was last updated by the legacy driver, the PRCATEGORY < 100.
Note: The specific value depends on what version of MSP the project was saved back with.
For MSP2010, PRCATEGORY = 14.
For MSP2013, PRCATEGORY = 15.
-- The Legacy driver is not supported with any later versions of MSP.