The people I know who’ve gotten to visit it so far were working on the project in some capacity (contractors, fabricators). It appears that the only way to get access to this before it opens to the public is if your work is somehow related to it. The person who offered to arrange a visit for me used to work in the arts/non-profits. I wrote to soon: my academic work is related to landscape and art, but I haven’t had the time this summer to make the trip out!