What one does know for sure that it has a Indo-Pak connection in the movie and many speculations around this have already been reported.
Now if sources are to be believed then Nawaz has been spending his last few days in Mumbai training for a special set of scenes for the movie, including some physical training too. This being because in all likelihood he is playing a ISI agency in the ovie who helps Salman's character and take the story further. Any other details so far is not known and will only surface when the shoot stars next week.
But to see Nawaz play an ISI agency would be rather interesting given his quick sense of humour and amazing screen presence which he displayed playing an interrogative cop in Kahaani.