Tom, I'm with JBD on this one. The main OCPD's in 2-100A panels fed by a single 45KVA XFMR aren't added together that way any more than you would count the 20A CB's in a panel to determine it's load. If the conductors to each are sized properly and the primary OCPD is less than 125% of the XFMR's rating, multiple panels could be fed depending on computed load. And I would also echo the comment to Tesla. It's the most common set-up but that doesn't make it the only code-compliant arrangement.
