Check out the net: bricks. The tables are made of slate (I think). They are outdoors all the time and don't warp or flake like plywood would. People arrive with their own balls and bats (paddles). And, some bring their own nets too. Otherwise, just line up the bricks, often slipped under the table.
Some parks are more geared to table tennis. Others are more for badminton. In this park the one's with shuttlecocks were relegated to the open area, without courts.