I've been contacting some bands, but I've been unable to get a response. The interesting and musically complex (AKA genius) instrumentation of math rock should translate amazingly into Rock Band. The only MR song that's been released that I know of is F.C.P.R.E.M.I.X. from GH3, which I have played to death. Since MR isn't very popular most MR bands are signed to an independent label, if they're signed to a label at all.
Some notable MR bands:
This Town Needs Guns - http://www.youtube.com/watch?v=lS56_MfEnrg
Giraffes? Giraffes! - http://www.youtube.com/watch?v=JZqZCS0rCmE
Piglet - http://www.youtube.com/watch?v=Op7AC4QndsE
The Fall of Troy - http://www.youtube.com/watch?v=_spVxhWEQWc
If I have any luck getting in contact with any MR bands, I may report it in this topic. The point of this topic isn't to merely to wishlist MR bands, it's to work toward getting some MR released, which, as far as I knnow, there hasn't been any released for a full band game yet.
What you can do: If you work with an authoring group, contact some MR bands and see if they're interested in the RBN. If you're not with a group, contact some MR bands and show your support for them getting material released over the RBN.