A Plano office tower has sold for one of the highest prices ever paid for a suburban high-rise.

The former Encana Oil & Gas building in Legacy business park sold for $123.3 million — almost $386 per square foot — to Dallas-based Tier REIT.

The sale of the 12-story high-rise comes five years after the tower last traded for an estimated $373 per square foot, or $120 million.

Tier REIT bought the 319,000-square-foot building, just east of Dallas North Tollway, from Arizona-based VEREIT.

The purchase includes assumption of a $66 million mortgage on the office building.

Commercial property firm JLL brokered the sale.

The 5851 Legacy Circle building is 88 percent occupied by tenants, including LegacyTexas Bank, U.S. Renal Care and Aimbridge Hospitality.

Tier REIT also owns 4 acres of vacant land surrounding the high-rise.

The real estate investment trust has drawn up plans for two more office towers with 570,000 square feet that it can build on the adjoining property. It calls the tower complex Legacy District.

"This acquisition complements our existing development parcels and enhances our vision for Legacy District, given its strategic location in the heart of the vibrant live-work-play Legacy submarket," Scott Fordham, CEO of Tier REIT, said in a statement. "Further, it plants our flag prominently near the exciting new corporate campuses of Toyota, JP Morgan, Liberty Mutual and FedEx Office, which combined should bring over 15,000 new office workers to the submarket."

The sale of the former Encana building sets the second-highest price in Plano's booming Legacy project.

Late last year, Boston-based Intercontinental Real Estate Corp. paid almost $140 million for the 2-year-old Legacy Tower at Dallas North Tollway and Legacy Drive. The 13-story Legacy Tower traded for just over $400 per square foot.

While high by suburban standards, the Legacy Plano sales are less than recent Uptown office building purchases for more than $500 per square foot.

Tier REIT hasn't announced plans to start another Plano tower, but the firm just broke ground in Austin on a 16-story, 324,000-square-foot office high-rise in the northwest suburbs. The tower is 98 percent leased to an Austin-based vacation rentals firm.