We're playing sceptics again today (you can tell because of the official sceptic-hat we're wearing) but according to Chinese MaxPDA forum member selith you're looking at a Nokia 5700 running BlackBerry OS 184.108.40.2065. Kicking off a fourteen page thread of people various praising his work and doubting it, selith then produced a video seemingly showing the handset in action.
From the Google translation it's difficult to figure out exactly what went on here, but we're presuming some sort of ROM tinkering that made the BlackBerry OS content with not only the Nokia's chipset but it's radio and other hardware. The short video only really shows browsing through the menus with the joystick, so it's not clear whether you can actually make calls.
[via Cloned in China]