The stayement from ATT is rather interesting. They ate not being allowed access to their equipment. https://about.att.com/pages/disaster_relief/nashville.html
Let me add something to this; this fascility may not be a POP at all. We know AT&T was NSA's largest FAIRVIEW partner enabling mass surveillance programs. Please read this article from the Intercept to understand what's likely happening there: https://theintercept.com/2018/06/25/att-internet-nsa-spy-hubs/
When reading pay close attention to: "They were developed under the leadership of an Iranian-American innovator and engineer named Hossein Eslambolchi, who was formerly AT&T’s chief technology officer and president of AT&T CTO"
From the article: images of other At&T national security buildings. Notice any resemblance? This is what leads to believe the building in Nashville serves a similar function.
Let's add another wild turn of events in Nashville. Airspace over the city has been declared "NATIONAL SECURITY AIRSPACE" prohibiting civilian aircraft from entry under the threat of being shot down. This further fuels suspicion of critical Intel or DOD infrastructure being there