Sure would help to know where you live. But, perhaps the grass is Arundo donax.

Probably a bit over-simplistic and not what you came to the OG forum for but ....
Why don't you simply go and knock on these people's door and ask them
1. what it is called
2. where they got it

you never know, they might even offer you a piece! :o)
A.

And let us know the name !!!

Ravena or Miscanthus Gigantus

You can have my Arundo for free! I've got Arundo and Variegated Arundo in containers that I still have to pot up or divide and I'm not looking forward to it. you ever see Arundo in a 1-gallon pot at the end of a full season? It splits the sides open with its culms. Freaky stuff -- very powerful.

It's ravenna grass most likely. I have it here and it's hardy in even zone 5. To divide that Arundo, sharpen up a hatchet, cut the pot off of it, and use a hammer to hit the hatchet through the roots of the grass. Or use a bandsaw. Easiest two ways I've found yet!
Sandy

I've got you beat, Sandy! I'm in zone 4b/5a and my Ravenna survives every year (and it's out in the open, not sheltered). I've seen it growing successfully well into zone 4.

Wanted:
Divisions of tall perennial Z4 grasses
Thanks
B