Much more is at stake than billions of dollars.
A national conversion to plastic pipes would amount to a massive experiment with public health because of the potential for plastic additives to leach out of the pipes into drinking water, and for hazardous chemicals to form in the event of fires, e.g., what happened in Santa Rosa CA last month.
From the article: "Studies have shown that toxic pollutants like benzene and toluene from spills and contaminated soil can permeate certain types of plastic pipes as they age. A 2013 review of research on leaching from plastic pipe identified more than 150 contaminants migrating from plastic pipes into drinking water."
"Plastics are being installed without any real understanding of what they're doing to our drinking water," said Andrew J. Whelton, assistant professor of civil engineering at Purdue University, and an author of the 2013 study. "We don't know what chemicals we're being exposed to."