The singer/songwriter will play stadiums this summer.
The deal also reunites the three-time Grammy winner with MCA Nashville for her music catalog.
One report puts the purchase price for the minority stake at $200 million.
The "Merry Go 'Round" singer-songwriter was the last artist signed to Lost Highway back in 2011, before it was absorbed by Mercury Nashville.
"By the time the song dropped, there was such pent up demand that the record exploded," says UnitedMasters vp of music/head of A&R Mike Weiss of "All the Way."
The label's first release is a track from rising Swedish producer Discrete.
New CEO Mike Harris and chief creative office Dave Cobb add Katie McCartney and Tom LaScola to their executive team.
“What we're noticing is that a lot of the old catalog means a lot to the new generation,” the producer says of selling the label's roughly 200-song catalog to Pophouse in January.
The rock label also signed Swedish power metal band Sabaton, In This Moment and Finnish rockers The Rasmus.
“As long as the artists I’m working with are equally or more passionate than me, I know they won’t quit on that dream,” says Atlantic’s Michael Parker.
