They showed a comprehensive film sequence of the fire as it progressed and really got working.
It turned out that with the combination of the lead roof AND the way that many of the beams (In that cruciform shape that held up the spire), There was no way thy could ven get water in there to do some good UNTIL large parts of the lead roof melted away. Imagine a lead roof. Th roof alone weighed in at about 50 tons they said(Im checking that out it seems rather light for a dense material over such an area and almost 1/2 in thick plating).
Wood beams are still among the most durable material to maintain shape in large spans,(so long as they are kept dry and protected from fire).
They are talking about using Titanium roofing because of its strength, workability with rolled seam technology, and its weight difference.
Theyve already got scaffolding repared and tehyre removing some of the concrete spandrels that had to stay while the repairs were going on.
Some of the new fire extinguishing systems especially made for institutions and historic buildings are some of these more toxic brominated organochlorines and Flouro chlorines. These things monitor where critical temperatures exist and the fire extinguishing chemical is pumped and sprayed right at it and the fire is extinguished rather rapidly.. We used to use "Nitrogen blanketing"for mine fires in coal areas but they have a small window of opportunity to work because after a point the sediments dissociate and the fire becomes almost self sustaining as it produces. its own oxygen.
They had an opportunity to install a water sprinkler and fire detection systems in the spire and attic but typical catholic church "calendars" they apparently decided to wait a few more centuries
BTW the Wed NYT had a large diagram of t Notre Dame Cathedral and gave a time line seris of all the repairs and additions through history. I think it was engineer who said that this place was futzed with since 1200 that its hardly a need to "restore it" to an original state cause there really wasnt one. Even the spire was a later addition and then was restored once before