How do private Internets works if the main line and outbound in bound switching centers are owned by big corporations loosing ground to private internet

Many of the undersea cables are owned by large corporations like samsung,vodaphone etc. These days many communities & cities are creating their own wireless internet but for the data to acess something on the other continent it has to go through these cables eventually so whats stopping these big corporations from stopping such data,offcourse encrypted data cant be but the end points of the packet are specified by the ip so how do these small private community grids plan to operate.