LIRR Pass 1905 - Good for Ferry - ID boat name?

What line were the third-rail-powered PRR MP54s built to run on?

Did they run on third rail to PRR Exchange Place? If so, why did that line have third rail? When did it lose it?

In Michael Bezilla's book "Electric Traction on the Pennsylvania Railroad" the first mention of MP54's is their introduction with the AC electrification from Broad St. Station to Paoli in 1915, and no mention of there ever having been any DC MP54's. Of course the PRR could have borrowed a few from the LI--they wouldn't have needed many--but with no third rail to Jersey City they could only have been operated from Penn Station to Manhattan Transfer.

Chris Baer's chronology on the PRRT&HS website states that the shuttle between Penn Station and Flatbush Ave. began on Nov. 27, 1910, replacing the Brooklyn Annex Ferry, and was discontinued on Aug. 31, 1911 (connections to PRR trains at Penn Station were not guaranteed); no mention of service between Penn Station and Jersey City. (The H&M was extended from Grove St. to Manhattan Transfer on Oct. 1, 1911, and to Newark Park Place on Nov. 26, 1911.)

For a full explanation of the operation replacing the Brooklyn-Jersey City ferry, see the thread "Electrified Tracks to LI City?" and click on the link in nyandw's post of Sat., May 28, page 6 of 12.