The rails you describe are called "takeoff" rails. They are for taking off the section car, either a handcar or motorcar (speeder, gang car). There were three types, the first was to store the section car at a section house or other facility like you have found. The second type were temporary rails set at a work site and would consist of not much more than the rails and just enough ties to hold everything together (2-4). The third type was really just a permanent variation of the second, usually at remote location (far from a convenient siding) or near a "problem" area that got frequent MOW attention. The later two types have all but disappeared with the introduction of Hi-rail trucks and the increasing mechanization of MOW work.
Depending on the situation, there may have been some sort of help for turning the handcar (or later the motorcar). This could be so basic as a few planks temporarily set on top of some extra ballast, through fixed planks, all the way to special turntable that stored between the rails. Most handcars and motorcars had handles that could be used to lever the car around at some convenient point like a crossing. Some motorcars had their own "turntables" (and many MOW machines do as well).
From my discussions with a former raodmaster of the B&ML, the run off rails were usually "scrap" or "broken" rail left over and almost never the same size as the main track (i.e. 90# main with 75# takeoff rails, or 75# main with 67# takeoff rails). There should be a slight down grade from the mainline to the section house for safety, it will be almost negligible (less than 0.5%), just enough to get the car to roll out of the way. The B&ML used the same size rail as its bridge guardrails for takeoff rails.
My suggestion is to find out what your was used in your specific instance, either by researching engineering documents, contacting the relevant historical society, by talking to former MOW crewmen, or even try discussing it with motorcar enthusiasts (like NARCOA).
Hope this helps...