Softbank, Free call between mobile phone and IP phone

According to the Nihon Keizai Shimbun news report, SOFTBANK will start a service called "white call" that makes free calls between mobile phones and IP phones in April.

Service that makes calling charges of mobile phones and IP phones free is this is Japan's first attempt.

Details are as below.
SOFTBANK, mobile - IP phone call free · within group

According to this article, SOFTBANK is offering IP phone "Yahoo! BB" Internet connection service "BB Phone"It seems to make calls between our mobile phones free.

The name of the new service is scheduled to be "white call", about 17 million mobile phone users of SOFTBANK MOBILE and about 5 million BB phone users. It is said that it aims to acquire customers widely.

Is it to enclose users by mutually utilizing IP phone, Internet connection business and mobile phone business? It is a place to worry about trends such as NTT docomo and KDDI to compete.