I looked this up once, and the answer is: They basically just ignore it. If everything is in a line, you just sync to your local phase, but if you have wires i

I looked this up once, and the answer is: They basically just ignore it. If everything is in a line, you just sync to your local phase, but if you have wires in a triangle that's impossible, and they basically just ignore it, in practice it doesn't happen often enough to cause any problems.