This is a subset of the actual peers that are available at each of the INXes; ie. only peers that are actively peering with the route collectors in each of the INX locations, will be visible here.
Other Looking Glasses
Additionally, Packet Clearing House also provide a different and historic view into each of the INXes that they connect to.
The Routeviews Project also runs a route collector at JINX which can be queried in various ways.