UP 4789

Whose railroad is this, anyways???  Union Pacific EMD SD70Ms 4789 and 4155 lead a southbound Canadian National (WC) freight train across the Lisbon-Pewaukee line.  SD70Ms are somewhat of a rarity on the UP in these parts, so what are they doing on CN?  Mark W. Hintz photo, 07/28/07, North Duplainville (Pewaukee) WI