There is Asian servers now.
how will they know?
Buggered if I know. I'm guessing it's just if people report a groups moving together not attacking each other. Same as your usual cheating reporting. People will just record footage of it then send it to whoever is running the servers then you'll get banned from the server.
It's also not the easiest game to work together in as you generally all start in different areas and make a dash for the play zone.
I remember when Day Z originally came out as an Arma mod. A few friends and myself attempted to team up in it. Problem is that you spawn in a random location and you have no map to tell you where you are. We all printed out maps of the Island then used road signs to figure out where we were to meet up. It was fun but it would end up taking hours before you finally meet up and by then a few of you would be dead.
PUBG does it different. The rounds last around 30-35 mins max and you spawn at random locations (kind of). You can see yourself on the map and report your position but if you spawn far away from the play zone then you're just sprinting toward the zone most of the time and don't really have a chance to coordinate unless someone spawns near you or in your path to the play zone.