It's all the work on the portion running alongside the Springfield Line that's under redesign after redesign, at extreme risk for lawsuit in West Hartford, and subject to potential additional extreme cost bloat because Amtrak hasn't worked out usage fees. About the only place that is "shovel-ready" is the New Britain Secondary from downtown New Britain to CCSU. And without the rest settled they wouldn't be able to continue building past Ella Grasso Blvd./Holly Dr. straddling the NB/Newington town line because it's the last side road access before joining the Springfield Line. So, whoopee, 2.7 miles out of 9.4 they can build basically across the 9/72 interchange, one neighborhood, a cemetery, and another highway interchange. That is by far the least costliest part of the project, with most of the work at existing CDOT expressway overpasses/underpasses. The Amtrak-running portion and the downtown Hartford touchdown are the defining aspects of the project.
Guess what: if Amtrak gets more HSR investment in the next Congress those usage fees for the ROW easement are going to skyrocket. They are getting a BIG gift from short-sighted CDOT to bide their time instead of...I don't know...this being negotiated as first order of business. Then there's the matter of the West Hartford lawsuit wildcard over the invasive overpasses and new intersections. And then there's the fact that any I-84 viaduct replacement will require destroying and starting over the downtown Hartford busway structures, meaning if that project gets expedited before the busway is sufficiently complete (say, by some big chunk of 84 falling off) then they're going to punt that leg.
If you want to know how cynical this project is, it basically all hinges on 1) beating the political fortunes of the Springfield Line in this Congressional environment before future Congresses' HSR investments pump up Amtrak's land value on the ROW and busway easement so much the lease becomes cost-prohibitive or Amtrak altogether reluctant to give them that much space, and 2) gambling on the condition of I-84 before the Aetna Viaduct replacement gets accelerated. Neither are happening according to plan because of all the design redrafts and other delays they're covering up. They can skirt on the PR as long as they can clear the land, trench utilities, do bridges and whatnot on the NB Secondary over almost entirely CDOT land and say "yaargh! The busway is HERE!" But outside of New Britain-proper it's still in grave danger in almost every stage of falling completely apart and getting ARC'ed. Malloy doesn't have to care, because he's probably not got ambitions to stay in the Capitol for 4 terms like Rowland/Rell and it'll be his successor's problem to kill it. He gets to milk the shovels-in-ground during his reelection campaign on the 2 miles of it that was never in doubt.
At least the NB Sec segment is too useless to even pave, much less partially open, without a connection at least as far as 173 near the Newington/West Hartford line. It basically can't operate as an open road to nowhere without the Amtrak and West Hartford crazy ramps settled, so there's little more they can do except prep the roadbed base, bridges, and utilities.