AIC rating for residential 100A main breaker
You'll have two services there.  

As you say, according to PG&amp;E, they design their facilities so that 10KA of short-circuit current is not possible for new single family drops. However, being a duplex with 2 meters, I could imagine them supplying twice the capacity. 

That would be 20KA.  Since only one service will have a problem at a time, the worst-case assumption is that each service needs to handle that independently.