The relationship between GTPlanet and SCEI is not that simple. Yes, GTPlanet is a significant part of the Gran Turismo franchise - a significant part that the game publisher has absolutely no control over. There would almost certainly be a few smiles around Sony's marketing/PR department if I closed down the site tomorrow. Sony wants to direct users to their web properties and their online communities (I have actually discussed this with them). They began realizing how much power and influence websites like GTPlanet can have over the brands that they control, and since that time we've been in direct competition as they continue to promote gran-turismo.com, the PlayStation.Blog, and the official PS forums.
In short, they have no incentive to provide me with 'exclusive' information, nor to promote or cooperate with GTPlanet in any way.