My quibble isnt with the word "taught", but rather with the overall wording conveyed in the title. As it is now, it seems to suggest that they've uncovered a hidden API where you can add custom grammars to Siri. A more accurate title would be, "RTM can sync with your iphone calendar". It really has little to do with Siri itself. Any calendar task will be synced, not just ones created by Siri.