the battery is disconnected the boot lid is closed. I need to open the boot to reconnect the battery.
I will provide an honest answer. I trust this will be appreciated. Please remember that a low rating PUNISHES me for being honest and that I receive nothing for my time until a positive rating is clicked.the answer to your original question is that there is no emergency release.
you can try applying jumper power via the jump start posts under the hood, this works on some years/models. if it does, it will power up central locking and you can release the lid normally.
other than this, if your vehicle does not have a key slot on the rear lid, then the only way to get in is to have BMW take apart the fuse panel and manually apply power to the wires that actuate the rear lid release.Please let me know if you have further questions. Please do not forget to click a positive rating as this is the only way I receive credit for my answer, thank you. Best wishes with your vehicle.