I did some research but could not find an answer to your question.  Suggest talking to the Volvo dealer or checking out Volvo's website, which may have more answers.

Sorry, I found this out just now -- MOST relates to the radio, it is a fiber-optic radio system.  Check out www.mostcooperation.com.  This is a mostly European way to interface optional stereo items with the factory radio, it has not caught on here yet, but is coming.