It could be that the stories of the commandos being surrounded in the hospital was an Israeli misinformation, intended to draw out Hezbos racing to join the fray and then get wiped out by these helos...
According to the Jerusalem Post the first wave of IDF commandos was intercepted and pinned down after they landed near the hospital. Reinforcements were sent in to extract them. From that point the operations was apparently so successful that the IDF had time to go thru the hospital, checking identities before safely extracting all soldiers and their prisoners. Not a single IDF soldier was even wounded.
http://www.jpost.com/servlet/Satellite?pagename=JPost/JPArticle/ShowFull&cid=1153292046965