The issue is pretty simple to diagnose. There's a locking/unlocking solenoid in the shifter. It's activated by stepping on the brake pedal. You should be able to feel/hear if it's working or not. If you can feel it clicking the shifter is no good. If you can't feel it working the BLS is probably no good.

The 220 S-Class doesn't have an emergency shift release. This is a necessary anti-theft feature since the 220 doesn't have a steering lock.