I don't think they are in the same circuit. I'll have to go back home
tonight and dig out my Rainbow to check (unless someone beats me to
it).
I can't be bothered to dig out the schemaitcs (I will do if necessary),
but I am darn sure the DPST switch in my 'Bows just breaks the live and
neutral wires of the mains supply to the PSU. It's a bit strange due to
the fact that the mains switch is on the fan bracket, while the mains
connectors are part of the PSU (so you have to trace wires through
various connectors), but electrically it does the obvious thing.
-tony