Use the free bmwconv command line tool to transform BMW iDrive multimedia data files (.br5) to standard Windows Media Audio files (.wma, which is what br5 to wma conversion basically represents. But you can also found other utilities that were designed for the purposes of br5 conversion.
Open BR5 file Open WMA fileA command line converter for BMW multimedia files
A BRX to audio converter
An audio data converter for Mac used to convert audio from BMW car system to MP3, WMA and MP4