Elisa Longo Borghini claimed the first maglia rosa as she led the squad across the line to take the overall race lead, the first Italian to do so since 2008.
They set a time of 20:05.99 over the 16.8km course to beat out Boels Dolmans by three seconds, while Mitchelton-Scott finished third, five seconds back.
“It’s a really special win," said Longo Borghini after the finish. "We’ve been targeting this race and especially this stage because it really suited the team.
"This is truly a team victory, and I wish I could share my maglia rosa with my five teammates because I wouldn’t be wearing it without them. It’s a really emotional moment for me. I had never been in this pink jersey before, and I have to thank everyone in the Trek-Segafredo team.
"I’m not a rider that wins a lot, and I think we deserved this victory because we have been riding so well as a team."
“It’s an emotional moment for me, although I don’t fully realize it yet since I have never been in this pink jersey, and never been in such a good environment with this team. I want to thank the entire team and everyone who was close to me during the lockdown."
The Giro Rosa has a recent history of beginning the race with a time trial, with the pancake-flat course around Grosetto almost a pure test of power, with little in the way of technical difficulties or climbing on offer.
The first team to finish in the warm conditions was Italian outfit BePink, finishing in 21:28.66 minutes. This time stood until being broken by Movistar who stopped the clock at 21:27.37 minutes
The Spanish team’s time in the hotseat didn't last long as Équipe Paule Ka bested their time by over a minute, reaching the finish in an impressive time of 20:15.08 minutes.
Most of the teams that followed could not reach this benchmark; only Mitchelton-Scott with defending champion Annemiek van Vleuten, the fourth-last team on the road, set a new best time of 20:10.45 minutes. Their time may have been faster still, but a ferocious turn on the front from van Vleuten dropped Lucy Kennedy and Moniek Tenniglo during an open section of the course.
Their time was further improved upon by Trek-Segafredo, posting a time 20:05.99 with just Boels Dolmans left to finish. They stopped the clock at 20:08.75, just under three seconds behind and confirming Trek-Segafredo as the victors.
SBS will have a daily highlights package from the Giro Rosa, broadcast daily from 4.30pm. You can also find the spoiler-free highlights here.