You can hear the Dallas Mavericks live play by play of their basketball games on your iPhone, iPod Touch or iPad from the TuneIn Radio app. From the TuneIn app, go to Sports -> NBA -> Dallas Mavericks Play by Play.
Also you can listen to the Dallas Mavericks on your iPhone, iPod Touch or iPad by downloading the NBA's official app called NBA Game Time app which gives you the ability to stream home and away radio broadcasts of all the NBA games and the Mavs once you upgrade to Game Time Plus.