My bet is on that there will be some kind of interaction of the metal catenary in the environment and maybe causing friction in the cables and shorts, which no one thought of since 1890 when they chose wood due for its insulating properties.
Then they will have to replace the metal with some fancy plastic one, because you can’t just admit the wood was better after all, but the plastic will also be unsuitable and degrade quickly which will ultimately end up with going back to wood in another 10 years. But that wood will then only last a fraction of the original wood, because we do not have old growth wood anymore and all the pine plantation wood won’t last a similar 130+ years.
So after about $3 billion dollars in costs and another $5 billion in economic and lifestyle impact after 20 years, they’ll declare it all a wonderful success, even though the wooden catenaries will live on as art or interior decor for another 200 years.
I foresee a "oh we can't replace the plastic one it with wood now because that would be a new material and we don't have data to prove it conforms with some rule we made up so the only solution is to pay some engineering firm who knows people on beacon hill a ton of money to say that pine is fine" situation before they go back to wood.
And as bad as the MBTA is... Keolis is worse (arguably).
