The Brooklyn Rapid Transit Company dates to 1896, when it started to purchase almost all of the existing trolley and elevated transit lines in the city, then borough, of Brooklyn. This cover is probably from the Broadway street car line which extended from East New York, along Broadway to the Manhattan Ferry docks. The line had already been in existance since he mid 19th Century. This cover however probably dates to the early 20th when a large power plant for the BRT was built a few blocks away on Kent Ave.
This is the large grid, raised line design used by a number of different companies in the late 19th and early 20th century.
The conversion of power for overhead trolley lines. Presently, unknown.
This cover is at the foot of Broadway at Kent Ave. At least one other example can be seen along Broadway, way up at Lorimer St, in Brooklyn, of course.