What's funny about reading this is how I can remember a discussion on these very forums from several years ago on the subject of the materials at the LoC. I came away from it thinking, "hmmm, I guess it's nice to know they have actual 35mm prints of the movies, but they'd be so faded by now and not really useful for any kind of restoration."
It's getting news like this that makes me happy I live in Northern Virginia.