I did read a little bit, since I got curious about it. From what I understand, they use transformers to step up the signal, convert to DC, it goes to transmission lines to a certain point, invert back to AC, step down, then goes the usual bussines.
My trouble with this were losses in the process of AC to DC and backwards. I can't seem to find anything on this. But I have a general understanding that the losses in the semiconductors are significantly smaller compared to those in transmission lines with AC.