I don't know much about Medical Assistant scope of practice, but I do know this: MA scope of practice depends upon a couple of things... state law/regulation (they do vary a bit), the clinical setting, and whether the physician has authorized that person to do those things after demonstrating competence. Some things, like blood draws, usually require evidence of formal training/education and perhaps a state-issued certificate for that. As a Rad tech, your co-worker may actually have that training.
Interesting question! I'm kind of wondering how it'll be resolved, because I'd like to know for myself!