-Chie's still pretty new on the whole and hasn't gotten promoted yet, so presumably all she knows about Ishimaru's dad is his name and that he's one of the big shots. His job sounds pretty similar to what our AU Commissioner Gordon does, and Chie knows him, so she probably knows him as one of Gordon's colleagues or at least a similarly-ranked person.

-Lenna would have been young around that time too, so it was most likely her father Alexander Tycoon who made the offer. He's a Councilman as well (and retired Ranger), and has recently gone missing from Union, presumed dead by almost everyone but Lenna at this point.