I do not think the substrate matters. Bill is using a non-gelatin coating, which should be able to go onto any clean surface. And with registration, one might be able to print multiple layers on the same piece of glass.

The article is two years old, and he is still actively working and experimenting, the best thing would be to contact him directly. I might be able to find an email address for him, but a quick search of my email did not turn up anything.