In this case the camera is just active image stabilization and a fast lens. The previous camera technology supporting the same name was a 42 megapixel monster that was down sampled to 8 MP. Although this phone uses the same name for the technology, the technology is not the same.
According to Nokia, they are making use of the pureview technology. It won’t be the 42 megapixel, but “only” 12 megapixel.
http://www.nokia.com/global/products/phone/lumia920/specifications/