My problem with the current plan for the project is the extremely high costs of long distance deep bore tunneling and the environmental impacts of going through the Scituate Reservoir, personally i think a better approach would be to split into two lines after New Haven, one heading up towards Hartford and Worcester to Boston, and the other heading eastward towards Providence to Boston a little to the north of the NIMBYs of the shoreline (think North Branford, Killingworth, etc).

With both of these routes using at grade, trenched, or elevated tracks whenever possible and only using deep bore tunneling when no other alternative is possible

As for Hartford to Providence (alongside Waterbury-Danbury-White Plains) I think that higher speed intercity Amtrak Regional service through Willimantic and Coventry RI via a restored Hartford, Providence, & Fishkill (a former rail line that ran from Providence to Fishkill NY via Hartford and Danbury) would be adequate for the distance and