There is no safe way to easily determine just what the ESC switch wires are connected to - if the question is asked on a forum like this, there is the danger of the responder taking the wrong part of a question that contains abiguities, however unintentional, and the asker also getting hold of the wrong end of the stick from what could easily be the right answer to the wrong question.
The switch descibed is usually a change-over switch (with its 3 terminals) plus, in the same box, an LED plus a resistor to let it work on the stated voltage.
With the switch "off", nc and common are connected. With the switch "on", no and common connect. If the contacts are strong enough, the switch can be inserted into the power leads of both ESCs.
I can think of no circumstances where I would connect the internal circuits of two boxes without knowing what the internal circuits were.