The CRRM is not ENTIRELY exempt from FRA oversight. It's still subject to Hours of Service regulations and the turntable is an FRA compliant structure. The way the law is written as I understand it is that a bridge in a railroad activity counts. For example the bridges on the cog railway are all subject to FRA oversight even though the whole railroad is not. With Mike Ramsey, we redid the Bridge Management Plan, BMP. I performed all the structural calculations on the bridge for the BMP.
Insular railroads like the CRRM, amusement parks, and operations like Como are in a weird area in the law. Aspects of them are technically governable but as I understand it its somewhat of a low priority in terms of oversight. Personally I think all railroad operations over 2' gauge that haul the general public should be subject to federal guidelines and regulations as they are a good minimum safety standard but that opinion and $5 will buy you a cup of coffee. Many of the laws that the FRA is in charge of compliance with were written long before or without tourist railroads and museums in mind, so many operations are outside the areas the laws were intended for when they were written.