I think the reason that you aren't supposed to have Ipods and such, is because the earbuds block off the sound around you, so you wouldnt be as able to hear sirens or commands given at random times. Boomboxes and such are ok because you can still hear what is going on around you. I assume that the answer is no, only because of safety reasons. ESPECIALLY since you are most likely going to be in the line of fire at some point.
I think No, but why not just ask your commanding officer. He/She would most likely know