no, i didn't get the wire with the x-surf version.
and nothing about this is mentionned in the documentation.
it's probably not needed because earthing is made thru the amiga pcb.
but of course, your amiga need to be connected on a earthed outlet.
for the moment, as my amiga are not connected to earth, i didn't tried external powered devices with the RR, and now i'm really too afraid from what i read here