Is it possible to add the power functions to Western Train Chase?
According to the product description on the LEGO® webn site, the LEGO® Power Functions Train Motor 88002, can be used to motorise the Western Train Chase.

The train wheels normally fit directly to this motor, so I'm sure that this train can be used on normal LEGO® tracks.

Looking at the instructions for both the Red Cargo Train and the Western Train Chase, I'd say that the magnetic couplings are the same height.