NEW YORK CITY and LOS ANGELES-A joint venture of SL Green Realty Corp.  and three other New York City-based companies has recapitalized the debt on the so-called Cabi Portfolio, a 31-property collection of Southern California office buildings. Total financing on the portfolio after the recap is $746.8 million, the REIT said Thursday morning, and the Blackstone Group is now the majority owner of the JV. Other partners in the JV include Gramercy Capital Corp. and Square Mile Capital Management LLC.