Ah, I see. I was going off memory that Arial existed in Open Office. After double-checking my sources (OpenOffice.org 3.2 running on Ubuntu 10.04.1) I see that I was incorrect in that. Nevermind, then.
Ubuntu doesn't ship it by default because of FOSS-wankery in the style of debian-legal — the Microsoft Core Fonts are perfectly free to redistribute in their original compressed form.
Not sure why not other open fonts, but hey, we now have three more, how's this not a good thing?
(Designed by Steve Matesson http://en.wikipedia.org/wiki/Steve_Matteson)