Summit Realty Group has taken over management of M&I Plaza, the 28-story office tower at the corner of Ohio and Pennsylvania streets that continues to battle back from high vacancy levels.

Summit assumed management May 14, replacing previous manager CBRE. The building, which is in the process of being renamed BMO Plaza, is the first multi-tenant downtown office tower in Summit’s property management portfolio.

Summit has been aggressively building the portfolio since launching its management division three years ago. In April, it landed the management and leasing contract for the 100,000-square-foot former Galyan’s headquarters in Plainfield. With the addition of the 673,000-square-foot M&I Plaza, it now has 6.7 million square feet under management.

The portfolio has doubled in size since Ken Petruska, Summit’s senior vice president of property management, joined the firm in January 2011. Petruska, who was hired along with three others from the former NAI Olympia Partners, brought some management contracts with him.

Summit's snagging the M&I Plaza contract is an example of how personnel moves can affect property management portfolios. Summit got the contract after the previous on-site manager of the building, CBRE’s Amy Pollock, was hired away by Cassidy Turley.

The building owner, White Plains, N.Y.-based True North Management Group, then hired Summit, which is keeping most of the on-site staff. That includes Nicole Langdon, who will be the on-site property manager. She was the assistant manager under CBRE.

Though Summit will manage the building, leasing is still handled by Cassidy Turley, which has been trying to land tenants after some key losses sent occupancy as low as 30 percent.

Cassidy Turley broker Jon Owens said about 53 percent of the building’s 435,000 square feet of office space is now leased. Owens said there are three proposals pending for all or some of the building’s vacant 23rd through 28th floors.

The 110,000 contiguous square feet is believed to be the largest single block of space available in the downtown market, which means that M&I Plaza frequently gets interest from potential tenants. “We see every deal there is to see,” said Owens.

By fall, he expects the property to officially go by the name BMO Plaza. M&I Bank’s parent company was acquired by BMO Financial Group last year. The bank that resulted from the merger, BMO Harris Bank, has its name at the top of the building, but the bank hasn’t signed off yet on rebranding the building BMO Plaza.

The bank continues to occupy the ninth and 10th floors of the 24-year-old building.