"It's a significant [complex] in a fantastic market," says Hines vice president David Perry. While acknowledging that the deal has closed, Perry declined to provide details, citing an ongoing confidentiality agreement. He adds that a press release will be issued within a few days on the purchase of the complex, which is also known as the Riverfront Office Park. Calls to Calpers and New York-based Blackstone were not returned by press deadline.

Despite that, industry sources estimate that the buildings sold for about $325 per sf, or in the $215 million range for the 667,000-sf complex. If accurate, that would reportedly be a new record for Class A office space in Cambridge, which has been a popular target among investors given the city's tight vacancy rate and rents that now average above $50 per sf. At present, for example, Beacon Capital Partners is entertaining offers from buyers angling to acquire its Technology Square office development a few blocks from the Riverfront site, while several other Cambridge office buildings have already changed hands this year.

The sale of Riverfront has created a domino effect as well, with Blackstone's property management team migrating across the river from Cambridge to One Boston Place. Blackstone and Walton Street Capital of Chicago recently purchased that 41-story, 770,000-sf office tower in Boston's Financial District for an estimated $180 million. Meanwhile, CB Richard Ellis/Whittier Partners has been hired to lease One Boston Place, which has a number of tenants rolling over during the next few years. Jones Lang LaSalle had managed One Boston Place for the previous owners, Lend Lease Real Estate Investments.