But analyst Ken Hoexter at Bank of America Merrill Lynch, in upgrading CP from "neutral" to "buy," said Thursday that performance gains and rising revenue prospects make CP shares a good investment.

Akerman wants to gain control of the board in order replace CP President Fred Green with former Canadian National President Hunter Harrison.

"While investors will continue to debate the benefits of Hunter Harrison versus Fred Green before the upcoming proxy vote [on May 17] we believe the company is posting improving performance, and current investors should benefit from a head start," said the analyst.