Some quick research brought this up...
250.184 Solidly Grounded Neutral Systems.
Solidly grounded neutral systems shall be permitted to be either single point grounded or multigrounded neutral.
""For systems over 1000 volts, the Code permits solidly grounded neutral systems that are either single-point grounded or multigrounded systems. For the 2005 Code, 250.184 was reorganized, and new requirements for the installation of single-point grounded systems were added. Circuits supplied from a single-point grounded system are required to have an equipment grounding conductor run with the circuit conductors, and this conductor is not to be used as a conductor for continuous line-to-neutral load.""
Text within the double quotes ("") is commentary from 2008 NEC Handbook.