I've seen it in 2 completely different residential areas here in Austin. One is very old and expensive neighborhood. Think pre depression era. The other in a 20 year old neighborhood. And not every house in either one. We have customers in both of them. Kinda a shocker first time I saw it.
There is 3 phase in the olmos park , alamo hieghts and a few other areas of San Antonio, a lot of people that did not know better did away with it but the wise ones still have it .there was a issue as to would the 3 phase systems use less electric than the high efficiency systems that qualified for the tax credit.