TWH raises a hugely important point when the service is ground fault protected and any other building on the system must have its' power distribution designed with this in mind. I recall the local coast guard station had a problem with a ground fault in the second building tripping the main. The solution was to remove the fuse for the O?C protection relays. That resulted in a failed overhead transformer and nearly cost an electrician some hospital time when a wire sock fell over the main bus.
Secondary buildings can be wired as extensions of the main service and do not necessarily have to be grounded at the second building (some exceptions). If the choice is to establish a new ground the ground fault protection scheme and the instrumentation to protect the serce equipment must also be designed to accomodate that. So the option always exists to bond the enclosures, remove the bonding jumper and isolate the grounded circuit conductor. regardless of the need for a grounded neutral at the second building it is still necessary to install it if the service is grounded. If the second building is not going to have any loads connected to the neutral then it may in fact be an expensive useless wire but in this jurisdiction it can be reduced but no smaller than the required ground. Then if neccessary it can be grounded.
