Azerbaijan and Missile Shields
Azerbaijan's foreign policy is based off trying to be friends with everyone and sell them oil and natural gas. Allowing everyone to use their radar station helps them achieve that balance, weakening the influence of the proximate and ambitious power, Russia, for one that won't care if they undermine Gazprom in the Caucasus. Here, as in Eastern Europe, Iran really isn't the key to the situation.
UPDATE: I hadn't realized that the Russian proposal was entirely based off Azerbaijan. That means the whole thing could have been proposed in the expectation the Bush administration will give it the cold shoulder.