I'm not Nee, but not sure if it's possible. I THINK (not 100% sure) it's a part of the actual .ui page Cui elements, rather than an .inc (UI include script), which probably just styles the ui screen layout.
I don't think that anyone at SWGEmu has created a proper UI editing tool, SOE's exists, but that's kind of 'taboo', so to speak.
EDIT: Just had a look at it within Sytner's IFF Editor tool suite. You could add a new Data parameter maybe, to link to a new loadscreen within ui_loading2.inc , which should control that loadscreen, so I guess it is possible.