If you want to know if they are ever
used by Theravadins, you would need to ask someone who knows all the regional variations ... might be hard to find.
More seriously, the butsudan looks nice ... any group that meets in a borrowed/multipurpose venue, or any individual who wants to keep some separation between 'sacred' space and the usual function of a room, could use one. And I know Tibetan groups use water bowls, but usually (AFAIK) a set of small bowls, not one fancier one.
Hope this helps.