Well, after my last post, I got a quick reply — and in English! — from Valerio Brambilla at the Biblioteca Ambrosiana. He was very helpful, which was a nice change.
Firstly, I learned that the BA is in fact a private collection! It is not state-funded. I didn’t know this; I wonder how many people do? The English language website is offline because they changed the company that provided it. The new prefect is Mons. Buzzi, and he told me that they have good relations with Notre Dame.
Unfortunately they seem to be obsessed with the possibility that commercial publishers may use materials they put online. This relates mainly to artworks in the collection of paintings. But in consequence they are trying to devise a way to put images there in a “no download, no print” manner. It’s understandable that they need to protect themselves from commercial exploitation; but not at the price of preventing access to the collection.