To answer you Benltrain ... Long Island City and Richmond Hill are simply the only two designated diesel yards for the LIRR. The great amount of the LIRR's equipment is electric and runs through to Penn Station or Flatbush Ave. A lot of the diesel Jamaica finishes go directly to RH as the HPA trains come to LIC yard.
The diesel layups in LIC are serviced, fueled, cleaned and inspected there. Inspections, heavy repairs and total toilet service are done in RH. The Yardmasters of both yards discuss what trains need to cycle back to RH each morning and designate their equipment trains based on that and consist needs.
The four third rail tracks are more for that "safety valve" rather than layups. Even the one train in the morning and one in the afternoon is inspected and cleaned elsewhere and simply is a "turnaround" in LIC.
Dave ... Did you know that those beloved power plant smokestacks have come down as per New York City despite neighborhood attempts to save them. When I retired it sounded like they were going to build a skyscraper apartment building on the site.