Dean,
You pretty well said it.
An "insular" non-FRA line would no longer be interested in purchasing this locomotive unless it is re-certified to ASME standards. This is probably not an issue unless CHS intends to sell/lease it to someone else in the future. Considering the lack of availability of any suitable narrow gauge locomotives, #12 will remain the Loop's steam work horse until the #111 is able to relieve it.
Federal rules (as in FRA) generally supercede any applicable state rules, so whatever changes are being made will have to meet FRA's approval before the Form 4 is approved.
I am not aware if CHS/Railstar maintain or are required to carry boiler insurance. I know there was a general liability policy for the Loop.