CP spokesman Martin Cej and CSX spokeswoman Melanie Cost told Reuters their companies did not comment on market rumors. Calgary-based CP has said it is interested in acquisitions as rail traffic surges on the back of the North American energy boom. Harrison, a former CEO of Canadian National Railway (CNR.TO), joined CP in 2012 after being hand-picked by activist investor William Ackman, whose hedge fund Pershing Square Capital Management owns a large stake in the company.