[cf0ed2aa-bdf5]

You are correct. They managed to gain access to the email account of one of the participants and simply used the information in the email about the conference call to dial in.

This is the email http://pastebin.com/8G4jLha8 and at the beginning of the recorded call you can hear the conference call software asking for the access code. ( https://www.youtube.com/watch?v=pl3spwzUZfQ)