For a while now this has only been a rumour on Wikipedia, but now the info has been updated on IMDB.
According to IMDB, Sandra Oh and her Grey's Anatomy co-star Ellen Pompeo have both been cast in a musical called The Goree Girls which also stars Jennifer Aniston. The Goree Girls is based on a true story of an all-female country band in a Texas prison in the 1940s. Sandra Oh is rumoured to be playing Vicki Cristine Rose, and Ellen Pompeo a character called Farrah.
Don't get too excited as there is still no official confirmation and this could change at any time, so take it for what it is peeps.
To read more about the real Goree Girls, Texas Monthly has published an article on them which is available here