Ed,
I don't quite see the point about about fixtures on A & B not being in phase with fixtures on B & C. The load on B phase will be twice the load on either A or C phase if you have one fixture connected A&B and one fixture connected B&C.
Working with volt-amps may be meaningful for calculating a transformer load, but in this case, I think the higher number is the correct one to use.
The use of amps in the calculation may be a code requirement if I'm reading things right. In the following order 220.10, 220.3(B)(2) .
Of course, I could be just plain stubborn here, after all, that's in the job description of "electrician."
Tom
[This message has been edited by Tom (edited 09-13-2002).]