This really annoys me when websites do this.
I don't have UA reservations right now to check the website, but a 'workaround' that usually works is to open one reservation/item, then if you middle click the 'back' browser button, the previous page opens in a new tab, and from there open other things in the same way. Not as easy as opening multiple tabs like usual of course.
Works with Firefox and Opera, I think on other browsers too.