Yup the wires from the 1940s/50s era used on those overhead distribution systems were uninsulated. They've generally been replaced by quadruplex when upgraded.
I suspect the system being stretched beyond capacity may have caused the sagging as the wires were running warm also, the very misty weather possibly doesn't help much either.
Those wires are normally very tight and wouldn't move about in a breeze at all. There's something very wrong with that set up. I suspect something's moved/slipped. They seem to be using spacers quite a bit in some areas too to keep them apart. However, in general they'll just come in and replace that with a run of very ugly quadruplex.
The system did trip after a while, but it took over 1 min.
Then again, if you search around youtube, you'll see quite a lot of footage of LV systems not tripping out for quite a while. Clearly the older systems simply weren't fused very well at all.
E.g. :
http://www.youtube.com/watch?v=cTDjq6K-qM4
