That doesn't make any sense to me as the car can just run on natural gas itself without having to disperse so much in the conversions leading to charge a battery:
ICE engines mostly generate waste heat, even when natural gas is the fuel.
Generating the power across town with the same fuel (in a turbine instead of ICE), transmitting it, converting it to DC to charge a battery, converting that back to AC and spinning an electric motor is more efficient. Yes there are more steps, but none of them are anywhere near as awful as ICE efficiency.
A combined cycle gas turbine is about 60% efficient, and you lose about 20% in transmission, converting to DC, charging, and converting to AC to run the motor.
A natural gas combustion engine is 40% efficient and loses 5-15% of that in the transmission.
https://en.m.wikipedia.org/wiki/Natural_gas_vehicle