I have Intellij ultimate 11.1, with the scala plugin installed.
I installed scala 2.9.2 using homebrew, which put scala in:
/usr/local/Cellar/scala/2
Change /usr/local/Cellar/scala/2.9.2 to /usr/local/Cellar/scala/ and you are good to go.
/usr/local/Cellar/scala/2.9.2
/usr/local/Cellar/scala/