Are Bus Lines Permanent vs. Streetcar Lines?

This photo was taken from the New York City Transit Museum.  It is from the Luden Collection and was photographed on April 16, 1948.   You are looking east at the intersection of McDonald Avenue and Cortelyou Road in Brooklyn.  The photographer is probably standing directly underneath the Culver Line ( main line ) as it swings north westerly.  The structure that you are looking at is the untracked ( except perhaps for the local Manhattan bound track ) connection to the Independent Subway that did not open yet.  In the foreground you can see the track shadows of the Culver El.  The connection to the Independent Subway was not yet put in place and would not be in operation until four years later  in October, 1954.  Notice the various wooden troughs for the trolley wires under the el on McDonald Avenue for the # 50 Streetcar.  Notice at right angles to the el structure, a broad wooden trough for the Cortelyou Road trolleybus (#23) overhead.
   This week, news came out that the mayor of the City of New York, Bill Di Blasio gave his seal of approval for a long waterfront streetcar line from Astoria Queens to Sunset Park in Brooklyn. To my surprise, there is not universal approval for this proposal.  One of the critic points is that a bus line can serve the same purpose for the fraction of the cost.  Some people say that bus lines can be eliminated rapidly while streetcar lines cannot.  The Cortelyou Road line started as a streetcar line on 16th Avenue.  In the early 1930's, the BMT corporation experimented with the first trolleybuses in Brooklyn on this line.  The wood trough above is probably when the line went into operation in 1932?.  To make a long story short, the line was bustituted on October 31, 1956 and remained a diesel bus line until a few years ago when it was completely ELIMINATED.  It is funny that the first trolleybus line in Brooklyn, probably which had many passengers was later eliminated when it was a diesel bus line. If a company wants to make an real estate investment, bus lines can come and go according to politics, but tracks and wires are difficult to ignore... but look what happened to also Route 23 in Phildadelphia:  Germantown Avenue.   More to follow later.