Six vs four axle loco

[Canadian Atlantic Railway]

I am not sure if it was on the Big Blue or another forum but a member had asked if six axle locomotives were used on locals or in yards. I came across this picture this morning of a GP15-1 and C44-9W doing some switching in Denver, CO http://www.railpictures.net/viewphoto.ph...285&nseq=1 If anyone else has any odd paired units please post