Herbert George's book "Change at Ozone Park" gives an excellent and detailed history of the Rockaway branches and the early history of the LIRR in general, including the beginnings of electrification.
The last train to Ozone Park, which is pictured on the rear cover of the book, consisted of five cars of the MP54 type, both arch roofed and monitor roofed, including one T54 trailer. The photo, taken from the roadbed facing the Northbound platform (which had become the only platform in service), shows a couple of passengers (apparendly a woman and a child) detraining from the rear vestibule, and the caption says the equipment and crew are preparing to deadhead back to Penn Station. After this, the third rail power was shut off and LIRR service on the Rockaway Beach Branch ended forever.
Had the fire not occured, LIRR service would probably have continued, at least for a while. The railroad had dickered with the City before about selling the Rockaway lines for subway service, and maybe this would have eventually come about. If not, remember that the LIRR and the City subway are now owned and operated by the same MTA, and so had the Rockaway branches continued as LIRR lines up through 1966, they would today still be operated as LIRR lines under the MTA. But as things developed, what evolved were three stub-end branches under (at that time) two railroad managements. The three branches became two, with the demise of the Rego Park-Ozone Park segment.
Herbert George's book ends with an angry epilogue. He says that in 1950, the tracks and right of way were still there, as were the personnel with the knowhow to move the multitudes of passengers. A way should have been worked out to publicly finance the rebuilding of the trestle and the resumption of LIRR loop service. But the bureaucrats in charge could only see incorporating the Rockaway branches into the subway. Passenger rail service to the Rockaways was saved, but at the expense of inefficient operation, much longer travel times, and inconvenience to the travelling public.