It means that each licensed system above 150 MHz must change to narrow band by 1-1-2013. For most folks, this means replacing older (usually 10+years old) equipment out that can't be programmed for the narrow band emissions. While moving to VIPER or other statewide systems is not mandated by the FCC, for many counties and cities, faced with replacing entire non-narrow banding compliant systems, it is a good choice. By choosing the VIPER option, they only have to change out subscriber units, not rebuild their systems, not to mention the interoperability benefits.
Dale