AT&T gas a number of these sites scattered about. Out in the sticks, on a hill top with a big parking lot and an entrance leading underground. Also some specialized antennas on the property.
Even if you know where they are, they are difficult to spot on a sat pic, as they are so low key.
They are not secret as the locals all know about them, and many were employed building them. One I have seen was called “the hole” by the locals.
My understanding is they are hardened communications sites,
Bell Laboratories had been working on EMP hardened communications networks decades ago during the Cold War.
Yes, and the Feds would not tell local inspectors or the tax office squat much less “oh by the way we spent $61,000,000 for you to tax us on”.
I think AT & T wants to be able to function after an EMP attack.