If you look at the BMW website under accessories, they offer a Sirius satellite retrofit via a software code.
That to me means that all of the hardware is there, whether you option to buy it or not.
They just want you to pay $350 extra to software enable it from the factory or a little more to retrofit via a code. It probably costs them next to nothing for the hardware.
Just make it standard already! Take away the 1yr free if that's burdening costs.