From my experience you usually see open delta
in an area where most of the customers are single phase, like a small strip mall.
I have set up a few computer rooms with this system in Naples Fla.
The biggest problem we had there was the single phase equipment in the computer room. You usually don't bring a neutral to a computer room panel so the electricians didn't pay much attention to which phase was which.
We ended up swapping some stuff around to get the phases balanced. You really can't put much single phase load on the wild leg, line to line without it drifting since it is only anchored in one direction.
The rest of the building had single phase panels for the normal loads
