Because Stirling engine depends on gas expansion and cooling, some practical problems are inherent in the engine. One problem would be to wait for several minutes before the engine warms before pressure builds up.
Winter time is a major wait.
I'd rather take the skytrain. Cooling the engine is a major dilemma because the gas has to be cooled to produce the necessary cycle. Not like in internal combustion engine where cooling is necessary to reduce over heating of the entire engine.