Is this any use: it's for the F10 with the same gearbox....
Here is the complete directions from BMW
On vehicles produced from 09/2010 or on vehicles updated with ISTA/D 2.39.0 or higher (target integration level from 10-09-500), the following procedure to electronically unlock the parking lock may be used if an engine does not start but the starter motor is still operational:
1) Turn the ignition ON (KL15).
2) Press the brake pedal and continue pressing it throughout all further steps.
3) Press the Start/Stop button (starter will engage).
4) As soon as the starter motor is engaged, press the unlock button on the left side of the GWS shifter and move the shifter forward to position N.
Note: For M57Y diesel engine-equipped vehicles and during low ambient temperatures, a certain delay (up to 4 seconds) may be experienced before switching to the N position.
5) Continue pressing the GWS shifter towards the N position until the audible gong is heard and a CC message "Gearbox Malfunction. Gearbox position P may not be possible. Activate parking brake while vehicle is standing" is displayed.
6) Then release the gearshift and reselect the N position within the next 6 seconds. Gear position N is then displayed in the instrument cluster.
7) Continue depressing the brake pedal until the starter motor stops cranking. Then the brake pedal can be released and the vehicle can be moved/pushed into a desired place.
Important:
After applying the procedure described above, the vehicle can only be moved manually. Towing is prohibited since the parking lock may engage, causing severe transmission damage.

The ignition has to be ON (KL15) at all the times during this process. If turned OFF, the Park gear position is going to be engaged automatically.
NOTE: If neutral position N cannot be achieved, cycle the ignition ON/OFF several times (press the Start/Stop button without depressing the brake pedal). Then try steps 1 to 7 again. After 3 unsuccessful attempts, a minimum 10-minute starter "cool-down" period is required before another try.
Alternative process
If the process above doesn't work, try this:
Doing some net searching, I found the following....
Apparently, our 8-speed auto gear boxes (sport or standard) have software to release the transmission using the lever.
1: Push start button or attempt to start the car (even if it doesn't turn over, just push it down anyway
2: Push the lever twice in to N
3: Push the lever to N and hold for 5 seconds
4: Transmission is now disengaged for 15 minutes after which it will re-lock itself.