I've also seen quite a few 120/240 Delta installations in Northern NJ, in fact I learned the hard way on my first experience with one in Park Ridge at a lighting store.
These services are also popular in North Carolina in 50's era homes. As a kid, I was always curious as to why they had two 4/0, a 2/0 neutral and a #2 for the third leg. Now I know why. The GP circuits, range, etc. are fed from the single phase 200A panel and the electric heat/HWH loads run from a separate panel using only the high leg. I am sure that dates back to the days when lower rates were offered for heat/HWH.
That is one beast that you need to tame before you touch it for sure.
With today's proliferation of DIY shows on TV and home centers, I seriously doubt that we'll ever see a new 3-phase service in a residence again. Even in high-rise condos, I'm sure that single-phase is all that we'll ever see. There's too much risk with Harry Homeowner.
