And why are there no lines, shortages, or high prices in Pennsylvania?
Because different places mandate different gasoline blends. So if a hurricane disrupts Gulf refiners when they were about to brew a batch of your state's blend, then you are out of luck.
It would make too much sense for the state to suspend the requirements so that any state's blend could be sold in NC.
Fact Sheet: Increasing Fuel Supply in the Aftermath of Hurricanes Gustav and Ike
http://www.whitehouse.gov/news/releases/2008/09/20080915-7.html
The EPA has waived certain fuel requirements in order to make it easier to use the supplies we have domestically and increase flexibility in what we can import. This waives requirements for gasoline sold or distributed in Alabama, Florida, Georgia, Louisiana, Mississippi, North Carolina, part of Ohio, South Carolina, Tennessee, Texas, and Virginia.