UP didn't "tear up" the old MILW yard. They tore out their own yard about 15 years ago and continue to use the ex MILW yard to this day. Here is a picture taken 7/8/2009 at the ex MILW engine terminal in the yard. Notice the excellent condition of the track.
The IERHS fairgrounds museum has a direct connection with the UP yard and can move equipment out via the UP. Presumably to get to the museum site in Reardan it would be interchanged to BNSF at Erie st then routed BNSF to Cheney and EWG to the museum site. They are committed to moving at least one piece of equipment out of the fairgrounds per year. They are busy laying track at the Reardon site to accommodate their equipment. A switch off of the EWG main was installed at the museum site last year. Here is a link to a video of the first train over the switch.
First train over museum switch