Re: FRA jurisdiction - You don't ask..

Sorry, you don't ask if the FRA wants to be your track inspector. They will excercise their authority if they believe it is within their jusrisdiction. CATS would fall under FRA jusrisdiction not only because they are interstate, but because they cross public highways.
In reality, the FRA inspectors are actually checking to see if you are in compliance with the applicable regulations, which are often subject to a wide range of confusing interpertation. The owner/lessor/operator is actually responsible for the regular inspections (track inspection at least twice a week if carrying passengers).
I would be very interested to see any known standard for 36" track. Some of the standard gauge requirements for gauge variation should translate assuming the standard wheel width tread is used. Other standards, namely surface variations could be different assuming you engineered them for the lower center of gravity, etc.