the passive entry on my '13 (bought in Dec '12) was part of the convenience group. i have the little buttons on the front door handles and do not need to press buttons on the fob to enter my vehicle. its like the corvette, just walk up and the car/truck recognizes the FOB and the doors magically unlock.
i would think this would be a big effort to install it on a truck that does not have it. and probably quite pricey if even possible.