I emailed a friend of mine who has a great deal of knowledge regarding LIRR history. His information supports S. Islander’s answer. His answer: Leased PRR engines were brought to Long Island by car float at Bay Ridge, Brooklyn. Their pilots were removed in the process. This had to be done when engines were loaded onto and unloaded off of car floats because the weight of the front of the engine would depress the car float when being moved onto and off of the pier. The PRR leased locomotives to the LIRR from 1900 until October, 1951, on a monthly basis as needs arose. In October of 1951 all remaining PRR-leased locos had been returned to the parent road with one odd exception occurring in August, 1955.
The K4s locomotives were used not only on runs to the Hamptons and Montauk, beginning with the construction of the much stronger "K4 bridge" over the Shinnecock Canal in 1931, but also ran on the Main Line and the Port Jefferson branch, and they ran throughout the year, not just summer. Also, some K4s locomotives spent a great deal of time on the LIRR and one in particular, #5406, was built by the PRR's shops and spent its entire lifespan in LIRR service until returned in 1950-51.
Hope my friend’s information sheds a little more light.
Andy
