the shop that i worked at in the '80s did it.
the trick was to make a loop of cable housing from a non-aero lever and run it up, back to the bar plug that was drilled for the housing to run through. then out near the stem. We only did it to SLEAVED bars so tht they had extra metal to help prevent failure.
If I remember right only 1 failed! Would I do it today? Hell no.