1. A mobile communication system comprising: a common radio base station capable of carrying out radio communication with both a first terminal joining a first provider and a second terminal joining a second provider; a common radio network controller configured to control the common radio base station for providing the first terminal and the second terminal with radio communications through the common radio base station; a common switching apparatus configured to carry out switching of a communication route for communications received from the first terminal and the second terminal via the common radio network controller wherein the common switching apparatus is able to turn back the communication route to a common radio network controller not connected to a public network side; a first management apparatus configured to manage subscriber information for the first terminal; and a second management apparatus configured to manage subscriber information for the second terminal, wherein: said common switching apparatus comprises a subscriber information obtaining part configured to obtain the subscriber information of a calling terminal by accessing any one of the first and the second management apparatuses, according to the provider which the calling terminal joins.