I am by no means an expert or even a rank amature in regards to what a broker will or will not release, but I doubt very much that Fidelity wouldn't release your address to a company you hold shares in. Especially if the company was trying to contact it's shareholders with info.
I am almost leaning towards it (post card) being sent to shareholders with a minium of x number of shares. Though I am sitting on more than a million shares I probably don't even come close to being in that minuim bracket based on the shares I know some used to be sitting on.