Bill Sweetman has in interesting insight into the corporate culture of Sukhoi.

The founder of the design bureau was not a member of the Communist party, and the deisgn bureau seemed to be routinely outmaneuvered in the Soviet era by the MiG deisgn bureau, Artem Mikgoyan was brother of senior politician Anastas Mikoyan, and Tupolev design bureau, which was always very tied in politically.

As a result, the Sukhoi design bureau is unlikely to be amenable to partnerships with its rivals, and tends to look outside the country for such deals, as evidenced with its recent work with India on the PAK-FA.