Looks like an older tower used for first responder agencies. And it's very cost effective to attach cellular equipment onto it.
Hughes Tower for example. Without any sauce it's hard to say if that's actually Hughes Tower but it looks like it might be.
That's not what it means. Any meaning to it is purely speculation.
There's nothing in US Flag Code for civilian use. There's nothing in military code, at least for Army and Marines. US Navy would not use that to communicate.
And the explanation provided defies any common sense. If we used the flag to communicate with the enemy then how the hell would the enemy know what this means? That's what parlays are for.
Show me a flag semaphore code that uses a single flag.
Is that a flag semaphore though? I'll grant you it's a single flag but it's the flag and color of it itself that has the meaning, and not necessarily a part of a code of communication.