Don't hold your breath for better service in the Metro. The last major update I've seen was a story in the Washington Post about half a year ago saying that the carriers were falling behind schedule and they would need more support from Metro to get the job done on time. If history is any indication, Metro is probably not up to the task. Even if it means missing the deadline required for 1.5 billion dollars of federal funding.
Although, officials have said that the work in 75% complete. The only problem is that service at stations cannot be switched on one by one. They need to switch on almost the entire system at once. For once, I hope to be surprised with Metro's efficiency and management.
http://www.washingtonpost.com/local/commuting/cellphone-service-undergoes-improvements-in-dc-metro-transit-system/2011/09/23/gIQAZhY7tK_story.html
http://washingtonexaminer.com/local/dc/2011/09/metro-falling-short-promised-cell-phone-service-upgrade/118681