What does BMT stand for in regards to the NYC Subway System?

Brooklyn-Manhattan Transit (corporation)

Elaborate:

The Brooklyn-Manhattan Transit corporation made up part of what is now known as the B-Division transit system in Brooklyn (the IND, or Independent Subway System, which was city owned and opened in 1932 made up the rest). Incorporated in 1923, the BMT operated the J, L, M, N, Q and R trains which have deep roots in Brooklyn while connecting to Manhattan over the Manhattan and Williamsburg bridges. The BMT was bought out by the city in 1940 and eventually incorporated into the existing IND. The B-Division now includes the following lines: A,B,C,D,E,F,G,J,L,M,N,Q,R, and Z.
Side note – the IRT (Interborough Rapid Transit Company) lines, which currently make up the 1,2,3,4,5,6,7 and 42nd St shuttle (now the A-Division) are unable to incorporate with the BMT or IND because the track width is narrower.

BMT

Reason For Asking:

I still see BMT plaques up in various places and was wondering if it was still an incorporation or if it was just memorabilia.

Source: Wikipedia: BMT
Source: Wikipedia: NYC Subways
Source: Wikipedia: A Division
Source: Wikipedia: B Division
Source: BMT Lines: History