The MID is the abbreviation for "Multi-Information Display." The MID is the device below the radio (the part with the tape or CD slot) that displays radio stations, time, date, etc. You also use the MID to set the car's on-board computer functions. The thing on the with the volume knob, audi/DSP, and telephone buttons in this picture is the MID.
If the MID is still installed, then the Bluetooth phone information would probably display. I am not sure how the BT phone modules sends its outputs to the radio, so it may be compatible through the ISO cable.