Windows phone (Lumia 1020) is probably the last place where you would expect to see Ubuntu, but a user has posted images with Ubuntu running on this device and they seem to be legit.
The first thing that users might think is that someone ported Ubuntu Touch for the Lumia 1020 device and that would not be an impossible task. It would be difficult but not impossible. It would also be a difficult to install a custom ROM, but that's also not impossible. The interesting thing is that the images show an Ubuntu system running and not the Touch version.
Running Ubuntu on a Lumia 1020 devices tells us two things. One is that the Linux kernel has hardware support for the specs of the devices, and the second one is that the device is powerful enough to run it. In any case, it's an odd choice and the only reason to do this is to show that you can. There is basically no practical application to this, besides the cool factor.