Fritz,
Interesting progress, and keep up the good work. Regarding; "right to operate over these public rights-of-way "forever". Remember that a public right-of-way is just that and in every State in America, a railroad can build across and use the space in the right of way same as anyone else. But that railroad must own property or right of access on both sides of that public street. A train is just as much a part of the public as the truck or a car.
In 1960 the crossing diamond rails was laying on the river bank just below the 13th and Cement Street location where the old route of the SNRR crossed the D&RGW-SG&N track access. Maybe you can dig it out of the river and rebuild the old allignment of the SRR To SNRR route up Cement ST.
The Val map I have show the SNRR track from a switch off its main trunk at 13th and Cement St connecting with Track 23 (D&Rg), crosssing the track 23 with a diagional diamond and also going down Cement St to 6th, turn 90 degrees right, up 6th and to the connecting to the end of the D&RG wye at 5th and Bluff Street. At that point notes (D&RGW) say AFE retired T-9536 1942, leading to North Star mill.