Judging by
http://www.beastiemania.com/discog/show.php?g=mixup
It looks they still might be going through their original run.
I am sure one of the more knowledgeable board members could answer this though (paging SirScratchaLot)
If you take this
virtual tour of Oscilloscope Studios it looks like a lot of copies of the Mix-Up are still hanging around in the studio.