No Titanic was filmed in Super 35 as all Cameron films (bar Aliens) are. Try and get a copy of Cameron's article on the aspect ratios of his films which he included in the Pan and Scan Laser Disc version of Terminator 2 (his preferred version.)
In this process, a large frame is filmed (top and bottom), in theatres, a middle proportion is used for widescreen projection, when it is converted to fullscreen VHS (and now DVD) the top and bottom of the film is exposed.
You can tell when a real panavision film is scanned for TV.