im pretty sure in a lease contract, it says you are allowed to tint it. and give it back with your tint.
i know my acura was fine. i was told to take the 30 percent tint off the whole windshield, but i didnt, and i didnt have a problem there either.
2006 325i Sparkling Graphite Metallic-Black Leatherette
Navigation-Bmw Assist Automatic-Xenons Carbon Fiber Front Lips-Aluminum Pedals Power/heated Front Seats
5% Tint all around 30% On windshield all the way down