In the mobile industry all the service providers and virtual operators are such examples. They get to use the physical networks of the incumbents for a governem

In the mobile industry all the service providers and virtual operators are such examples. They get to use the physical networks of the incumbents for a governemnt regulated price in most markets, to create competition an make sure the incumbents are not exploiting the natural oligopoly in the mobile industry (due to the cost and feasibility of several players with nationwide antenna-coverage).