I recall the news articles about possibly rerouting HAZMAT shipments, but the Indian Head line is certainly no longer a possibility. Long out of service, its rail were lifted in January 2008 and the right-of-way is now a paved Charles County trail.
When the 2005 BRAC called for transferring more personnel into Fort Belvoir, there was a suggestion to extend either the Blue or Yellow line of Metro to the post, and there was an illustration in the Washington Post showing where each line would run. The proposed Blue Line extension would have run down the old Army right-of-way.
An article titled "New Use For An Old Right-of Way?" in the January 12, 2010 issue of the Fairfax County Times noted that “military leaders have slightly more than 90 days to submit plans for use of the $150 million in federal funds just approved for transportation improvements around Fort Belvoir… All parties are in agreement that the bulk of the funding should be used to widen Richmond Highway (U.S. Route 1), the gateway to the fort, to six lanes. However, other key details remain in flux, including the scope of the widening… Fairfax County officials are also very interested in improving transit access to Fort Belvoir. [U.S. Rep. James P.] Moran (D-Dist. 8) said a study of the possible reuse of an abandoned rail bed that connects Virginia Railway Express tracks to the fort could potentially be paid for with the new federal dollars.”
Interestingly enough, an employee at the post's civil engineering office told me in early 1993 that there was interest in extending VRE service down the line (the tracks were still intact at this point) as far as Route 1. At that location, the old warehouses next to the tracks on the west side of Route 1 would be demolished and replaced by a combination bus-rail terminal with a bus loop. Buses could come up Route 1 and deliver inbound commuters to the terminal in the morning and take them away in the evening. I asked about extending the line further into the post, since such a terminal would be a long walk from just about everything on Fort Belvoir, and he said no, that long-term plans called for the widening of Route 1, and that meant the rail bridge would go. As we know, no extension of either VRE or Metro service has ever taken place, the post railway tracks are long gone, and those old warehouses still stand. Since there's no money to put rails back down on the old post railway's right-of-way, I suspect the only thing we'll see there are more vines, trees and briars.