It's just like any other connection. You can think of the wifi links just replacing a cable. If NYC Mesh are linking through fibre installed at various building

It's just like any other connection. You can think of the wifi links just replacing a cable. If NYC Mesh are linking through fibre installed at various buildings around town then yes, anyone with access to that router could snoop. In Germany, the Freifunk mesh project solved this problem by routing through VPN tunnels: https://pinneberg.freifunk.net/en/faq https://pinneberg.freifunk.net/en/faq