Metro was supposed to have all of its underground tunnels and stations wired for the major cellphone carriers by Tuesday but riders may end up waiting as long as three more years.

Metro has remained publicly mum about whether it will meet the deadline. "We are obligated to provide an update to the Hill by next Tuesday. We won't be able to comment prior to the letter being transmitted," spokeswoman Caroline Lukas told The Washington Examiner.

But the transit agency lobbied Congress earlier this fall to give it an extension on the deadline linked to $1.5 billion in federal funding, as The Examiner first reported last month. A Metro memo said the agency and its cellphone partners won't be able to finish the work until Dec. 31, 2015.And it's going to "necessitate additional shutdowns of major portions of track" to complete.

Congress did grant Metro an extension until March 27. The local congressional delegation has plans to push for a longer extension in coming months, as the cellphone requirement was not the intent of the original funding plan.

It is not entirely clear why the work could end up so delayed. Metro met the 2009 deadline to install service at the 20 busiest stations.

In the Washington Metropolitan Area Transit Authority's 2011 annual report to Congress on the status of the installation, General Manager Richard Sarles gave no direct mention that the agency wouldn't meet the deadline. It had finished 82 percent of the 27 remaining stations as of October 2011, according to the letter obtained by The Washington Examiner. He said that underground fiber was 78 percent finished, while aboveground fiber was 52 percent done.

"We have made progress over the past year, but still have significant installations needed to complete the program," the letter said. "While the timely completion of this project is important to WMATA and to our customers, our most urgent priority is maintaining the safety and reliability of our system."

Jack Corbett, who leads the advocacy group, called the delay, and the lack of an explanation from Metro about what is causing it, frustrating.

"A lot of riders expected the law would be followed and they would have full service through all the stations, not just the 20 busiest," he said.

Corbett is wary of people chatting on the phone the whole ride, so he thinks the transit agency should remind riders to be courteous. But he said having the service is important for riders, especially when a train breaks down. He said he's seen half a train's riders pull out phones when a train gets delayed to alert their office they'd be late. "It's very frustrating to be stuck at a station that doesn't have service," he said.

Metro board member Tom Downs recently noted that Metro's emergency alert plans rely heavily on emails, phone texts and Twitter messages. But, he said, the agency shouldn't act like riders can get that information anywhere. He said Metro needs to show where riders can't access cellphone service.