That picture — how do we know it's the real path that the aircraft traveled, and not just an arbitrary interpolation of the flight's radar info from flightaware.com?
That would depend on what data they used. If you go to the Passur
LaGuardia airport monitor, and re-play starting at 15:26, you will see the following track, which appears to follow a slightly different route. In particular, notice how the helicopter is turning right to avoid them (it is a helicopter, even if it appears as a plane on the image), which it wouldn't do if 1549 was to their right, over the highway, as that other picture suggests.
