I had problems getting our non-iDrive stereo to read iPhone music via the USB and it turns out the BMW supplied cable was bad - dealer replaced it and now it works. Our car is pretty bone stock, so yours should be fine too. We were using a 4s. Also, if you just put MP3s on a flash drive and plug that into the USB port the car will automatically read them too... pretty nifty.
2013 X1 sDrive 28i, M-Sport package, Mineral Grey