Correct. Standard e-tube plugs fit in the "sprint shifter port" of 6870 and 9070 shift levers. The "brains" are in the shift lever, the sprinter port simply functions as a remote button.
If you cut a e-tube wire in half, strip the insulation off, plug it into the sprinter port, and short the wires together, you get a RD shift. Which "direction" the RD shifts depends on which lever you plug in to.
Splice on a momentary switch (Cateye buttons work great but there are heaps of options) and you have remote shifting where ever you desire.
I've been considering something like these momentary membrane buttons for a TT cockpit setup but haven't made much of an effort beyond buying the buttons and wiring up a test arrangement. They actuate the shifts just fine, but the "stickers" need a flat surface on which to mount in order to function properly.