http://creators.rockband.com/
In short, anyone will be able to put any of their songs (song's they've written, played and recorded that is) in the game. Watch the video on that page and it will tell you all you need to know.
News Breaking Article...
I charted it out for my FoF project. watch it in HD for better audio sync and quality. Using the demo track off of the redux. This video is not meant to showcase what little skill I have, simply the chart I made. I hope you guys like it, and I hope it is accurate enough XD