This looks like a smoking gun to me, by establishing that the Naudet-FDNY team must have had foreknowledge:
They had a SECOND camera within sight of WTC, ALREADY RUNNING at 8:46, specifically to record our the victims' first wince of shock and awe. It was shot on the same street (Church) as their FAMOUs 8:46 footage, but 11 blocks closer to their bosses' crime. (Cross street here is Murray rather than Lispenard.)
They never identify the nature of this clip, but it is plain on examination. And as creepy complicit snuff film makers they couldn't resist sneaking it in under our noses.