On Cedars video he suggests that it is someone within Bethel has leaked the information and makes an address to the GB stating that they have Brothers at Bethel who are prepared to leak information and to remember that these are people that they sit down to a meal to eat with.
Surely the letter has already been printed and ready to send out, I don't see why someone in the printing department, who isn't high up, would not have easy access to this.