I dunno if your figures are correct, but if so it would seem that a substantial fraction of that 50% "loss" could be recovered in a turbine when the gas was used.Partial oxidation of natural gas to an alcohol would be more efficient than losing 50% of the energy to compress the gas . . .
I never saw an 18 turbine in an 18 wheeler. Natural gas is OK for stationary engines but I don’t think I would ride a bus powered with that much high pressure fuel. Propane is different. Both are more dangerous and flammable than Diesel.