No voltage between phases means voltage is not present? EXCUSE ME?????
Maybe ... just maybe ... this is the wrong panel for the service. It's time to start over.

CHECK YOUR ASSUMPTIONS!

How many wires are coming in from the PoCo? How many transformers do you see on the pole?

B and C leg will show no voltage between them if they are both powered by the same leg. Yet, they'll still read 120 to ground.
I see this when someone puts a 3-phase panel in a 1-phase location. (As Solar Power described)