From past experience, as a helper at the time. If I can recall correctly you need the 2 hour burn on all critical feeders.Which seems to me in a hospital all patient care areas. I remember using M.I cable for this a few tears back. I'd have to check my code book for the article numbers, thisis just off the top of my head. Also seems to me most hospitals I've done work in have panels dedicated to critical loads, usually having generator back up.