Mac, The LDC side of your utility operates at relatively low pressures... ie 30 psi in the mains and 7 psi at the residential customer.
Natural Gas transmission systems like Snam, operate at 600+ psi. You can't use plastics at these pressures and cycles.
While discussing the pressures at the city gate flange (steel) , also ask the LDC guys what happens with hydrogen embrittlement ... and if your LDC is in the hydrogen business?