It seems that the MTA's plan for the Second Avenue Subway is to build it in segments. The Daily News' sources say the first phase would be stops at 96th, 86th and 72nd Sts., then "the trains will curve west to 63rd St. and Lexington Ave. and south on express tracks underneath Broadway through the tunnel also used by N and R trains. Some trains would continue into Brooklyn." Construction, expected to begin next year, is estimated to take 10 years for $4 billion. The MTA is building the line in segments, in order to win more federal funding (Washington is wily and wants to see part of the subway actually up and running before commiting bucks). The entire project is estimated to cost $17 billion, finishing construction somewhere around the year 2020.

But for Gothamist, the best part of the article was finding out some people call a less–than–Manhattan–long subway line a "stubway."

Gothamist on the Second Avenue subway.