O2 (Ireland) BT Group and 1 mm02 share for each British Telecommunications share they held. After the de-merger, most of mmO2's operations, including Digifone, were rebranded O2. mmO2 plc later became O2 plc and remained an independent company until 2005. On 31 October 2005 it was announced that Telefónica, S.A., the Spanish telecommunications company, had made a recommended takeover bid for O Ireland's parent company, O2 plc. This was then approved by shareholders and O was officially purchased in mid February 2006. The O2 brand is now used in several countries for Telefónica's mobile operations outside Spain and Latin America, where Telefónica
O2 (UK) certified with the Carbon Trust Standard in recognition of its commitment to reduce its carbon footprint. O2 attained the standard after saving 47,000 tonnes of carbon over the previous three years through its energy efficiency measures, including a £1.4 million distribution of smart metering technology across the company's cell sites, offices and retail stores, and upgrades to more energy efficient systems across its mobile phone network. In addition to distributing energy efficient LED lighting and boiler system controls, the company was also able to reduce energy use by removing air conditioning units from some of its cell sites and reducing