The cellphone carriers installing wireless phone service in Metro's underground subway system warned the transit agency a year ago that it needed to do more if they were to meet a federal deadline to complete the work.

The carriers said in a letter obtained by The Washington Examiner that they would need an "augmented effort" from Metro, including making sure safety escorts did not show up late and could actually do the work they were getting paid $305,000 a month to do. (See the letter in the embedded viewer below this story.)

Yet the entreaty does not appear to have worked: Metro and the carriers missed the Oct. 16, 2012, deadline, leaving riders with spotty cellphone service underground likely for three more years. The lack of coverage has been confusing for riders as Metro has not publicly addressed the delays. The incomplete service also represents a safety concern, one member of Metro's board noted, as Metro increasingly relies on communications sent to mobile devices to alert riders of problems.

A Verizon executive sent Metro General Manager Richard Sarles a letter dated Oct. 13, 2011, on behalf of the carriers outlining their concerns -- plus 12 steps that should be taken to meet the looming deadline. It is not clear if Metro addressed any of the concerns, though the blown deadline suggests the transit agency did not do enough to fix the problems between the two entities.

"That letter is more than a year old, and since October 2011, we have made significant progress working with our wireless carrier partners to advance the project," said Metro spokesman Philip Stewart.

When asked to explain the progress made, Metro pointed to a letter it sent to Congress last month. But that letter said the work likely won't be done until late 2015, nearly twice the time it was supposed to take under a 2008, $1.5 billion federal funding deal.

Melanie Ortel, a spokeswoman for the carriers, declined to comment Tuesday about the delays.

The Verizon letter cited "organizational issues" on Metro's end that limited workers' access to the tunnels. The carriers said safety escorts arrived late or Metro did not provide any or enough of them for requested work. They said other equipment blocked work zones and escorts arrived unprepared. Metro took 100 or more days to approve work as the plans bounced around various departments, which the carriers called "simply not acceptable."

Additionally, the carriers were paying for work that did not get done. They had agreed to pay for 40 dedicated escorts to work 40 hours each per week in February 2011, the letter said. But the carriers were not going to be able to use them all despite paying about $305,000 a month until at least May 2012 due to Metro training rules added after the funding agreement.