I have a Giro D' Italia Cinelli bars that game with my Montello when I bought it as the third owner. It has holes on the bar where the tops of the lever bodies land, when installed and on the reinforcing sleeve on both side of the knurled surface for the stem to clamp on. First I thought it was a home made jobbie, but after examining the way the holes were drilled, I determined that it was done by Cinelli at their factory as it looks like you need to use specialized drilling equipment to come up with the unusual angled extended mousehole shaped (domed on one end and flat on the other) profile the holes near the stem has. I also saw another example in the net with exactly the same shaped holes, further evidence that Cinelli did issue bars with holes drilled for routing cables in them. I guess eventually they just went to the grooved bar design that must be much easier to produce and does not bring up the question about possible structural compromise from drilling the bars.....
the GDI bars now live on my just completed Bottechia. The brake cables were a bit of a challenge to install, but after doing one side with the help of some string and a powerful vacuum cleaner, the other side was a cinch after that....