Further to my post above and in response to earlier posts that pointed to a DMV web page which lists the vehicles that qualify for a CSF plate, I just asked DMV this question on their FB page and received the following brilliant response:
VirginiaDMV Good morning Alex. We no longer publish a list of qualifying vehicles by make and year however, you may contact the Virginia Department of Environmental Quality at 703-583-3900 or toll-free in Virginia at 1-800-275-3844 for more information on qualifying vehicles. Here is a link to more information available on our website regarding qualification criteria based on clean special fuels:
http://ow.ly/WTDea (click on "How to Qualify") Please let us know if you have any questions. Thanks so much.
Virginia Department of Motor Vehicles
Welcome to the official site of the Virginia Department of Motor Vehicles, with quick access to driver and vehicle online transactions and information.
DMV.VIRGINIA.GOV