Yeah, that's probably a better thing to say since the Masoretic Text is in Hebrew for the OT. The NWT says 'hey, we'll put in Jehovah whereever the author quoted the Hebrew scriptures and the Hebrew originally had the Tetragrammaton', and Paul apparently quoted a lot from the original Hebrew texts.
Interesting wikipedia article the changes: http://en.wikipedia.org/wiki/Masoretic_Text (look under Scribal emendations)