Regarding the Summit interchange with the Rahway Valley:
The tracks used for this are among those still intact in the 'lower' yard. The RVRR came in over the now missing bridge onto the track next to the wall. Interchange was held on the next track over givng RVRR essentially a run around track arrangement to come in pull forward and drop cars into the west end. They could then pull out, drop back and grab inbounds from the west end of the second track and depart down the hill again. The switch and track to the bridge were intact well into the 1990's.
The ex-EL interchange at Summit and the ex-CNJ interchange at Cranford were both embargoed by RVRR President & General Manager Bernie Cahil shortly after the creation of Conrail in 1976 in favor of the ex-LV interchange in Roselle Park. He saw no point in going to 3 places to connect with the same railroad and needing to maintain the line to Summit (which had no online business past Springfield) or the CNJ leg past Crossfields(?) who got an occassional tank car (that and sometimes car storage being the only use of that part of the railroad by the early 1980's till DO took over and starting going down that side to access the SIRT.). Post embargo Conrail delivered a couple of Monsanto hoppers to Summit - Mr. Cahill refused to accept interchange and Conrail was eventually made to bring them around to the ex-LV interchange.
Other than per-diem boxcar storage in the mid-80's the last past Springfield use of the RVRR main was for passenger specials to the US Open at Baltusrol in the summer of 1980 or 81. Those trains were sponsored by United Counties Trust Company and an on-line customer whose name escapes me using the RVRR engines, and RVRR boxcar with a generator and three passenger cars (including the dome car and business car) from Delaware Otsego.