Very similar conclusions to a 2021 article in Vox:

2021 Vox article by Jerusalem Demsas:

> the researchers were able to identify a few reasons for what happened to the Green Line: Jockeying between two different understaffed agencies with little experience managing large projects and consultants, a laissez-faire approach to allowing stakeholders’ expensive ideas to be added to the project scope “even if impractical,” and public pressure for more as the project dragged on and the demand for transit options increased.

This Slate article by Henry Grabar:

> when the Massachusetts Bay Transportation Authority got to work on the Green Line Extension, the agency only had a half-dozen full-time employees managing the largest capital project the MBTA had ever undertaken.

Demsas's conclusion in Vox:

> American transit agencies need to be staffed up in-house to reduce reliance on expensive contractors and build up institutional knowledge.

Grabar's conclusion in Slate now:

> the conclusion is not just the old left-wing bromide of investing in the public sector. Consultants are paid in public money, after all. It’s a philosophical shift toward an empowered, full-time civil servant class. Spending money now to save money later.

The similarity is because both articles cite Eric Goldwyn from NYU's Transit Costs Project, and because Goldwyn is right.