Actually Tony, if you tilt the camera at the focal plane your images aren't likely to line up very well. You need to rotate about the entrance pupil of the lens. A lot of sites mistakenly call this point the "nodal point" (as I used to).

They may have used a tilt/shift lens to correct for perspective, making it a lot easier to stitch together three images taken at different heights. Or it could have been corrected in software.