I believe that ILM shot the effects for the pilot on widescreen film, as evidenced by the recreated credits seen on an early trailer:pittrek said:
The interesting thing is that all the remastered special effect shots are widescreen
http://picasaweb.google.com/102542760950977079734/TNGHD
You'll notice that the two "new" close ups are actually reuses from the shots from the credits, and the long shot is mostly CGI so they rendered it in 16:9 to match the others. The other preview shots (using effects NOT from the opening credits) have been cropped, as the Blu-ray is. Also note in the shot of the planet that you can see the left most edge of the film and the new planet comes out from behind it!
What still bugs me is that they rendered ALL the new TOSR shots in 16:9 for some reason.