I have a copy of OoS in 5.1, as a DTS-CD, and I have been looking for others with no real results. I purchased the Limited Edition box of The Resistance, which should be here in a couple weeks, and it contains a 5.1 mix. I found a download of Absolution in 5.1 but it did not work, and I found another of BHaR in 5.1 which was a dead link. If anyone knows where to find these, I'd love to find out. I must admit that the OoS 5.1 mix is not particularly good, but I would imagine The Resistance will be awesome, considering it's an official release.
From my understanding, OoS, Absolution's 5.1 mixes are upmixes made from isolating individual tracks from the stereo recordings, which would explain why the OoS one does not sound like Muse-quality engineering. To be fair, for one of my favorite bands, the engineering wasn't stellar on OoS or Showbiz, but they're still amazing albums. I really want Absolution in 5.1 most of all.