Attached is the form used in Chicago...
From the form: 120/240V 3-phase, 4-wire
I didn't know you could still get that setup. Do they mandate one and only one service entrance per building?
IIRC, from another version of the form, that configuration was not available in all jurisdictions.
A co-worker who was doing volunteer electrical work at his church (an old building) was surprised to find that connection.
Essentially, a delta winding with one leg center-tapped, CT to neutral.
His surprise was finding the third node at a higher voltage (wrt neutral) than 120 V.
I don't believe there is any requirement for only one service entrance per building, especially since large commercial buildings may well have multiple customers, each with its own meter.
At my pre-retirement employer, there were two Edison transformers, one supplying the original building and the other supplying a later addition (continuation of the original).
Each transformer had its own switchbox indoors: the first was Square-D and the second was Siemens.
The two transformers were mounted near each other, where the utility easement was on the property for the underground feed cable.