I just the other day got a new offer from Plaza for February through April and it mentioned that the Bier Garten was opening soon. It did list a website for it at https://www.biergartenlv.com.
I walked in there yesterday and checked out the menu - the bartender said they have a limited menu for now, but it should be a full menu in another month. Right now they have 3 sausages, at $7.99 each IIRC, and a few other items.
Further update. My December trip is a long way off. https://www.vegaschatter.com/story/2014/2/4/181321/3919/vegas-travel/A+Bier+Garten+Now+Awaits+At+The+Plaza