Granted the article is poorly written, leading to confusion as to sequence and the referent "film," but I gathered that Moore's crew had interviewed Bergn not that Moore has wound up w/ unseen footage of Berg held captive. Either way, one would think the authorities would be interested, that they should have a look.
Ahhh, you're right. Moore did interview Michael Berg for his movie, salon.com has an article about it now...
--
"Moore interviewed Berg for "Fahrenheit""
"The murdered American hostage had given an interview for the documentary, but it is not included in the final version."
http://www.salon.com/ent/feature/2004/05/27/fahrenheit_911/index_np.html