 Virgin Media O2 is a planning to launch a new fibre-building joint venture with its owners Liberty Global NASDAQ:LBTYA and Telefonica to challenge BT Group PLC LSE:BT.As Openreach subsidiary in the high-speed broadband market, according to news reports. Liberty Global and Telefonica, which created Virgin Media O2 in a 31bn merger last year, have begun talks to raise hundreds of millions of pounds from third-party investors to fund the rollout of fast fibre broadband to 7 million more British households, according to Sky News. 