Natural gas predominately displaces coal, so you must really hate the earth.
Same with other classes of vehicles such as VW vans in the passenger version, the 'normal' ones are all diesel, the fleet version tends to be bi-fuel with a relatively small petrol engine and an LNG underbody tank system. This is a popular solution for taxi fleets in Europe.
And as diesel is coming more and more under scrutiny you can expect the LNG/CNG version of these cars to gain in popularity.
A rounding error compared to all the other trucks/vans/commercial vehicles.
Go look for CNG vehicles from pickups and airport vans on up to heavy trucks on the heavy equipment section of CL and machinery trader. You will see how few and far between they are.
Sorry man, but that’s nobody. 5k trucks a year is meaningless when we’re talking about how natural gas prices will effect behaviors.