2 options: Active: he has a server or service where if he doesn't check into or send an email to, passwords and instructions are sent to his collaborators.

    Passive: he has collaborators whom he actually trusts, and who will open the contents and release if something fishy happens to him.

My bet is on the former as it limits the odds that his contacts could 'defect' and release the contents early which would limit his leverage (assuming that this plan actually gives him any).