49 CFR Part 230, are the US steam locomotive boiler regulations and cover only locomotive boilers. Mechanical and safety appliances are covered under separate regulations. In a nut shell, US boiler rules are 1472 days with pressure in the boiler and fire in the firebox, or 15 years, whichever comes first.
The boiler for C&TS rotary OY is not a locomotive boiler, so does not come under FRA jurisdiction. It falls under Colorado or New Mexico boiler regulations. Generally state regulations are more lenient than the FRA rules.
Michael Allen