German ISP United Internet belongs to the select band of companies, along with Rakuten and Dish, that are planning greenfield national mobile networks to expand their core businesses. There has been much focus recently on delays to the build-out by the firm’s mobile subsidiary 1&1, which it has blamed on tower partner Vantage Towers, rather than its plan to use an Open RAN platform provided by Rakuten Symphony. But in United Internet’s recent earnings call, CFO Martin Mildner was focusing on what he says is an undersung positive in the 1&1 mobile business case – synergies with its fixed broadband sister company, 1&1 Versatel. Versatel focuses on B2B customers and is “one of the most hidden champions in our group”,…