The Lackawanna stopped using the screw fasteners in the 1920's, but there were some side tracks on the NY Division that still had them into the 1970's, at least.
The Lackanna used its own standard of rail sections, including 101 DL, 105 DL and 118 DL, into the 1930's. They finally adopted 131 RE before WW II, and continued on with 132 RE.
Up through 1968, the P&D Branch was mostly laid with 101 DL jointed rail, and it had seen many moons and many trains. EL still owned the rolls for 105 DL rail, and as long as the rolls were available the steel mills would roll anything a railroad wanted. So EL bought enough 105 DL rail to relay both tracks between Morristown and Denville with continuous welded rail in 1969, releasing enough 105 DL relayer to just about rid the P&D of that 101 DL rail. The 105 DL rail was a pretty good rail section for light MU and passenger traffic.
The Erie had adopted AREA standard rail sections in the 1920's, and stayed with them through EL and into Conrail. Most of the Erie's rail since about 1925 was in the 110 RE family, including 112 RE and 115 RE when they were developed; and the 130 RE family, including 131 RE and 132 RE when they became the standards.
Even though the newer Lackawanna and Erie rail sections (131 and 132 RE) were the same, the two railroads used different drilling patterns for the joint bars. It gave us fits when a piece of DL drilled rail had to be used for a replacement on the Erie in the middle of the night, and the section gang had to scare up two compromise joints to accommodate the different hole sizes and spacing.
The Erie also stuck with single-shoulder tie plates, with screw spikes in the corners, for a long time. That was not a good standard compared with the double-shoulder plates on the Lackawanna, and in the long run it cost the EL a lot of unnecessary rail running and tie deterioraton.
The Lackawanna management seemed to place a higher emphasis on good engineering standards than did the Erie. Part of that can probably be credited to the Chief Engineers themselves, and I would love to have been a mouse in the woodwork at the board meetings when engineering standards and their costs were discussed. Most railroads did not bother their Boards of Directors with such mundane topics, but on the Lackawanna the Chief Engineer, by virtue of his position, was a full member of the Board of Directors. That alone tells us a lot about their concern with engineering issues. George A. Phillips was the next-to-last Chief Engineer of the DL&W, and a Board member. He was known on the railroad as King George IV, and his word was Law.
One of his engineers was John Hiltz, who had come from the PRR to become Engineer Maintenance of Way on the Lackawanna. One of his pet projects was maintenance of extremely tight alignment standards on curves. He developed curve lining to a fine art, and taught it to the track foremen and supervisors. Most of the Lackawanna track supervisors in the 1950's had been curve liners for Hiltz, and had gone through the school that he taught personally. Of course, much good training on other subjects was passed along, too.
J. P. Hiltz later followed William White to the New York Central as Engineer Maintenance of Way, and then to the D&H as Vice President of Operations. When White went back to the Erie Lackawanna, Hiltz became President and General Manager of the D&H, and he filled both positions with great competence. His time and mine on the D&H only lapped by about six months, so I never had the privilege of this, but he was known to come back out on the railroad after a business car trip and check out the locations where he had a bad ride. He would have the Track Supervisor and the Patrol Foreman take either end of the string around the curve while he recorded the mid-ordinates. Then they would go sit under a tree and calculate the throws to get the line corrected. I don't recall if he helped drive the stakes, but he could have if he wanted to. Not many railroad presidents got their jollies from lining curves by hand.
When I was Asst. Division Engineer at Hoboken 1968-70, all four of our Track Supervisors were former DL&W, and they were excellent track men. They had all come up under Phillips and Hiltz.