I did smart pigging and challenging pipeline stuff years ago and reliability engineering up to a few years ago, also got out of o+g for similar reasons.
Totally agree and just adding on to all that, even if it was steel, I'm super willing to bet it'd be impossible to run a normal pig through, so much infrastructure is just full of diameter changes, unbarred tees, really tight back to back bends etc, I can only imagine the challenges to pig a line like that, let alone costs involved with specialised tooling and support work, I know some people who did a short run through a downtown core on a gas main and that needed hot taps, road closures and a really special pig for what was less than a kilometre.
Supposing it could be pigged without blowing up their entire maintenance budget, I wouldn't want to touch any of the water coming out of that line during operations, so you'd also interrupt water service for a while, having a solid reaction plan really would be one of the best solutions.