Nokia Maps, formerly Ovi Maps, is planning an escape from its melting Symbian cage to a new home on Windows Phone handsets. The above screenshots (leaked by istartedsomething.com) show that Windows Phone users can look forward to Microsoft’s Metro UI for maps – meaning they'll not only have access to London Underground transport lines, but also turn-by-turn navigation – all for the grand price of free. The native Nokia Maps app will be a shoo-in for Nokia's forthcoming Sabre and Sea Ray handsets, which'll arrive packing Windows Phone Mango. But will Nokia's ace mapping software be available for Windows Phone 7 users with non-Nok hardware? There'll be a fight brewing with Google Maps in the Android Market if it is.