I don't think it will take as long as mikerowe thinks for a major railroad to name a female as CEO. Former NS CFO Kathryn McQuaid moved to Canadian Pacific in 2007 as Chief Operating Officer. McQuaid now the railroad's Sr. VP and CFO. Also in Canada, Zoe Yujnovich, 37, serves as President/CEO of the Quebec North Shore & Labrador RR, a major ore carrier. Here in the US, Malisa Somers is President/CEO of Transtar, the holding company for US Steel railroad and barge interests.
Several shortlines have (or formerly had women) as GM's or COO's. Mass transit operators including Chicago's METRA have or formerly had female CEO's.