One EGC for all the circuits is OK.
250.122(C) Multiple Circuits. Where a single equipment grounding conductor is run with multiple circuits in the same raceway or cable, it shall be sized for the largest overcurrent device protecting conductors in the raceway or cable.
Not sure the power company will be happy with the feeders from 4 different meters to all be in the same conduit.
[This message has been edited by iwire (edited 09-17-2005).]
