This article from Workers World offers the following account of the takeover of the Moss 3 prep plant:
"On Sept. 17, 1989, the UMWA had seized the property of the Pittston Coal Co.'s Moss 3 preparation plant in Carbo, Va. Ninety-eight miners and a minister, outfitted in camouflage, pushed aside shocked Vance security guards and occupied the property. A giant spotlight propelled by a generator focused on the Pittston walls, where a giant sign spelled out 'United Mine Workers of America.' When the light went on, over 200 miners and supporters cheered and thousands more came forward to bar state police from entering the grounds.
Cecil Roberts, then vice president of the UMWA, addressed the crowd: 'Welcome to ... class warfare in southwestern Virginia.' For over three days they held the property, until Pittston agreed to a contract protecting jobs and other benefits. Pittston feared that the miners were planning to run the Moss 3 plant."
My understanding is that the strikers left the plant because of Judge Williams' orders of September 20 and 21, 1989, and that the strike continued through the winter and did not formally end until February 1990. See generally Clark v. International Union, UMWA, 752 F. Supp. 1291 (W.D. Va. 1990).