Third quarter profits at Japan’s smallest mobile phone network Softbank grew by more than six times, boosted by the November Hong Kong Exchange listing of Alibaba.com, the B2B marketplace for goods manufactured in China. Net income rose to 46.7 billion yen ($438.2 million) in the third quarter, up from 7.49 billion yen ($70.4 million) a year ago. Operating profit climbed 9 percent to 92.4 billion yen ($868.9 million). Earnings at its mobile phone unit were down. While Softbank is Japan’s fastest growing mobile phone network, it has stolen market share from NTT DoCoMo (NYSE: DCM) and KDDI by aggressively slashing plan costs and offering deep discounts and free content (earnings release in PDF form).

Earnings Highlights Include:

-- Income in the mobile phone division decreased 5.5 percent to 53.8 billion yen ($505.7 million) in the third quarter, with sales slipping 5.6 percent to 406.1 billion yen ($3.82 billion). 

-- ARPU decreased 1,040 ($9.76) yen from a year ago to 4,520 yen ($42.43). Softbank blamed the decrease on subscribers taking up its lower priced offering White Plan, as well as discounts it offered to subscribers on its New Super Bonus Plan.

-- Data ARPU, however, increased by 160 yen ($1.50) compared to the third quarter of the previous fiscal year to 1,490 ($13.97), and now contributes to 33 percent of total ARPU.

-- Softbank added 561,000 new customers in the third quarter, while rival KDDI gained 337,700 new customers, and DoCoMo signed on 208,800.

-- Sale of Alibaba.com shares in November contributed 57.2 billion yen ($537.9 million) to net income.

-- The broadband division saw profits surge 46 percent to 11.3 billion yen ($106.2 million). Fixed-line operations posted a 1.38 billion yen ($13 million) profit, compared with a 2.6 billion yen loss a year earlier.

Meanwhile, Softbank chief Masayoshi Son said that Microsoft’s (NSDQ: MSFT) $44.6 billion proposed bid for Yahoo (NSDQ: YHOO) could enhance the value of Yahoo’s brand, according to Bloomberg. The mobile carrier has a 3.9 percent stake in Yahoo, and owns 41 percent of Yahoo Japan. Yahoo search is the defacto mobile portal for the network. Reuters reports that Son has not yet decided what to do with its Yahoo stake, but “has no intention” of selling its Yahoo Japan stake. He also said Softbank, which has partnered with Microsoft in Internet telephony, “had no such plans right now” to counter-bid for Yahoo.