The changeout program is administered by the American Lung Association. According to their FAQ the funds are coming from Dominion Energy due to violations of the Clean Air Act:
"
Background: This project is a result of a settlement between EPA and Dominion Energy for violations of the Clean Air Act at three of the utility’s power plants in Illinois, Indiana, and Massachusetts. To their credit, this project will significantly improve air quality in the region by replacing old, high polluting and inefficient wood stoves with new EPA Certified wood, pellet and gas stoves."
(broken link removed to http://www.lung.org/associations/charters/northeast/woodstove/faq.html)
Looking at the settlement, they may have chosen counties that have directly been affected by the polluting coal plants of Dominion:
http://www2.epa.gov/enforcement/dominion-energy-inc#mitigation