Canonical took to the web to show off its new mobile operating system which functions and looks so much like Ubuntu, they had no choice but to call it Ubuntu.
Not to be confused with Ubuntu for Android, which is a version of Android running special Ubuntu software and allows for a full Ubuntu desktop experience upon docking, Ubuntu for phones is the actual OS which seems to replace Android as we know it all together. Canonical says that the device should be able to run on a number of smartphones as it uses the same drivers as Android. This is made possible as Android recently re-merged with the rest of Linux and now various Linux distributions can take advantage of what Google has put into Android.
Currently, Ubuntu for phones is only available (read: seen working) on the Samsung Galaxy Nexus.