I assume you mean this one:

http://www.secure-medicine.org/public/publications/icd-study...

You would need to be specific about which one of the linked documents you meant, there were several. All the hacking attempts started off with a manufacturer's programmer and worked back from there. In the example using a software radio, the researchers were able to replay sniffed commands to the device after it had been activated by the programmer.

Which of the reports talked about a device being compromised without using a manufacturers programmer?