Clarification:

The document calls out a two phase connection on the utility side:

"The traction power loads are single-phase and are being supplied by single phase power transformers with their primary winding connected to only two
phases of PG&E’s three-phase system, also known as a phase-to-phase
configuration."

So two phases of the utility system take the load, not one.

The document mentions a 115 kV railway substation. Yup, that's a common transmission line phase to phase voltage. If the substation tapped one phase only, it would be 66 kV.

Took me a long time to find this thread again. :(