I dont know how its done but my university routers are connected using lan cable and even though there are multiple routers I through out the network I only see one wifi network ...
That does not seems like mesh, as mesh is mostly wireless. It seems like they have wired all these routers in AP mode and connected them to a main switch. This can be achieved pretty easily.
What's more interesting is if you have something like unifi dreammachine pro along with there Poe switch, you can wire APs without any hassle with just 1 wire as it supports Poe. You can also wire Poe cameras to the switch itself which is really great for these applications. The AP along with cameras and other smart home gadgets can be great but the minimum setup for this cost around 1.3lakhs in India!!!!!! Just because of customs etc. And so is only good for enterprises.