These terminals are what I previously referred to as H/C contacts. And those mentioned packets are sent by HCE80 when closing and opening these terminals.
I do understand that it possible to implement this as in the diagram you have provided. But from all the advertising of new evohome features I was sure, that evotouch should be able to change the mode of HCE80 wirelessly.
Using wireless relay, to control another wireless device through the wires when both are controlled from the same wireless controller… I wonder what kind of genius designed this.