It sounds like, in general, a scanner can't handle the density of an analog negative; having posed the quesiton on DPUG.
That makes sense, given the horrible exposure capabilities of most flat-beds.
So in the end, it might be a moot point, but any investigation would be worthy nonetheless.
Here is the thread I assume you're referring to, though it was originally created to discuss calibrating negatives for papers/print processes. Is this it, or is there a better one?