Center tapped delta (Hi Leg) usually seems to be in smaller light industry places and the PoCo does it to save a transformer. 3P wye needs 3 but they can do center tapped "Delta:" actually called "Delta Vee" with 2 transformers. Typically one will be a larger size. If you see this, it is Delta V and the B phase is 208v. A to C is 240 with a center tap.

[Linked Image from gfretwell.com]

Greg Fretwell