...I was just the first to make a big deal about it!
There are actually a few working scale Grand Union Intersections that I know about. The first GU I saw (but I don't remember where) years ago was fully modeled but only part of it was working, the rest of the intersection was just for show. But then in the September 2010 issue of Model Railroader, a fully working O scale GU showed up:
This Grand Union Intersection is part of Les Lewis's home layout, the Connecticut Co. Notice the controls for the intersection on the lower right. As I understand it, the buttons are interlocked to prevent collisions. Press the blue button and the car will proceed straight through the intersection. Press the yellow for a right turn. Green for left turn, and press the red button to stop the car.
Modular Nuremberg. The remarkable thing about this GU is that the rails are insulated for two rail operation! Here is a video that has a snippet of a tram negotiating a left turn through it at the 10:24 mark.
So, sorry my friends, I'm not the first to complete one. But they sure are fun all the same. If you know of anymore, let me know and I'll post them here. Yes sir! Let me know!