I can't promise it will work well in Blackberry devices and I don't plan to add official support for Blackberry, but you can give it a try pretty easy and see how it works out by adding this to your user.config file
<add key="MobilePhoneUserAgents" value="iphone,ipod,android,iemobile,blackberry" />
Note that I'm assuming that the user agent string for Blackberry has the word blackberry in it, I don't know for sure if it does.
We're lower casing the user agent and checking if it contains one of the words separated by commas in this setting and if so we apply the mobile skin.
Hope that helps,