In 1941, the Boston Elevated Railway bought the BRB&L right of way from Day Square to Revere Beach for use as a high-speed trolley line similar to the Ashmont-Mattapan High Speed Line; these plans were delayed by the onset of World War II.
However, the 1926 Report on Improved Transportation Facilities and 1945–47 Coolidge Commission Report recommended that the East Boston Tunnel line, which had been converted to rapid transit from streetcars in 1924, be extended to Lynn via the BBRB&L route rather than using it for a trolley line.

In 1947, the newly formed Metropolitan Transit Authority (M.T.A.) decided to build to Lynn as a rapid transit line, and construction began in October 1948.
The first part of the Revere Extension opened to Orient Heights on January 5, 1952, with intermediate stations at Airport and Day Square, and to Suffolk Downs on April 21, 1952.
The second phase (cut short due to limited funds, and possibly due to the Eastern Massachusetts wielding its influence to protect its business in Lynn) opened to Wonderland on January 19, 1954 with intermediate stations at Beachmont and Revere Beach.
All stations from Orient Heights to Wonderland were located at the sites of former BRB&L stations.
The line was renamed as the Blue Line in 1965.

Although recommended and studied several times since, further Blue Line extension to Lynn has not moved past the proposal stage.
The former right of way from Revere Street to Point of Pines is owned by the Massachusetts Electric Company, a National Grid subsidiary, and used as a utility corridor.
Most of its length is covered in brush or wetlands, although several residential buildings and parking areas incur on the utility-owned right of way in Point of Pines.
The Alternatives Analysis / Draft Environmental Impact Statement, released in 2011, considered two potential routes: one following the Narrow Gauge right of way through Point of Pines, and one sharing the Newburyport/Rockport Line right of way.
In 1941, the Boston Elevated Railway bought the BRB&L right of way from Day Square to Revere Beach for use as a high-speed trolley line similar to the Ashmont-Mattapan High Speed Line; these plans were delayed by the onset of World War II. However, the 1926 Report on Improved Transportation Facilities and 1945–47 Coolidge Commission Report recommended that the East Boston Tunnel line, which had been converted to rapid transit from streetcars in 1924, be extended to Lynn via the BBRB&L route rather than using it for a trolley line.
In 1947, the newly formed Metropolitan Transit Authority (M.T.A.) decided to build to Lynn as a rapid transit line, and construction began in October 1948. The first part of the Revere Extension opened to Orient Heights on January 5, 1952, with intermediate stations at Airport and Day Square, and to Suffolk Downs on April 21, 1952. The second phase (cut short due to limited funds, and possibly due to the Eastern Massachusetts wielding its influence to protect its business in Lynn) opened to Wonderland on January 19, 1954 with intermediate stations at Beachmont and Revere Beach. All stations from Orient Heights to Wonderland were located at the sites of former BRB&L stations. The line was renamed as the Blue Line in 1965.
Although recommended and studied several times since, further Blue Line extension to Lynn has not moved past the proposal stage. The former right of way from Revere Street to Point of Pines is owned by the Massachusetts Electric Company, a National Grid subsidiary, and used as a utility corridor. Most of its length is covered in brush or wetlands, although several residential buildings and parking areas incur on the utility-owned right of way in Point of Pines. The Alternatives Analysis / Draft Environmental Impact Statement, released in 2011, considered two potential routes: one following the Narrow Gauge right of way through Point of Pines, and one sharing the Newburyport/Rockport Line right of way.
Boston, Revere Beach and Lynn Railroad