If the logging RR was/is not a common carrier, then the FRA laws would not apply In the days that logging RRs were common, OSHA as we know it did not exist. Safety rules would have existed maybe but much less stringent than we have today.
Logging RRs have a reputation for building their own equipment. Look for the book on the "Mann's Creek RR" it has a lot of stuff on a narrow gauge logging operation. There is some really crude homebuilt cars shown in photos in the book. I think disconnect logging buggies would not be home-built however.
As brakes, again the common carrier status is probably the most important. I tbink if a common carrier, there may be a requirement for air brakes after a certain date. If a private RR, then they could run with no brakes or hand brakes. Obviously, in hilly mountain country, some sort of brakes were necessary.
I am familiar with steel mill RRs which in many cases are private RRs not common carriers. And equipment that does not go into interchange service does not have to meet rules. Many Steel mill operations bought old gons especially, and maybe flats for in plant use. One of the first things they did was cut off all the brake rigging. The plants were generally level and trains short, so engine brakes were enough. And the big reason was that the stuff always needed maintence that they did not want to bother with.
