While owners of common stock will be cashed out, Prime Group Realty Trust's preferred B stock will remain, with six quarters of accrued dividends being paid. The vote in favor of the sale was expected, as four entities as well as the company's executives and board of directors own 60% of the common shares. In addition to paying $172 million for the common stock, Lightstone Group is assuming $426 million in mortgage debt as well as the debt represented by the 4 million preferred shares.

Lightstone Group acquires Prime Group Realty Trust's joint venture interests in the 1.5-million-sf Bank One Center at 131 S. Dearborn St. and the 1-million-sf R.R. Donnelley Building at 77 W. Wacker Dr. The REIT owns the 1.5-million-sf IBM Plaza at 330 N. Wabash Ave. outright. In the suburbs, Prime Group Realty Trust's most prominent asset is the three-building, 841,000-sf Continental Towers complex along the Northwest Tollway in Rolling Meadows.