According to Beijing MTR Corporation, operator of Beijing subway line 4, it has entered into an agreement with China Mobile Beijing to bring the company's mobile phone signal into the subway's line 4.

Under the agreement, from the opening date of the subway line 4, China Mobile's mobile phone signal, including the TD-SCDMA signal, will be available in the public areas and tunnels of this line. This is the first time for this Chinese-grown 3G standard signal to cover the subway of Beijing.

A representative from Beijing MTR Corporation told local media that the company attached great importance to the introduction of mobile phone signals into the subway line 4 from the beginning of its construction. At present, the two parties are implementing discussions and cooperation in bringing more mobile phone services to passengers.

So far, mobile phone signals are available in all the eight existing subway lines in Beijing, including the five underground lines. Of those, the subway line 5 was fully covered when it was opened in 2007.

The new subway line 4 has reportedly started some trial operations on June 20, 2009.