Charlie
They normally use the new SD75Is for head end power on the Santa Express. Sometimes they use the SD40-2s but not very often. The second unit you see is a converted FB unit that has been modified to be a steam generator to supply steam to the passenger cars for heating. Pictured below.
Other locomotives operated by the ONR are GP38-2s, GP40-2s. Up until a little while back they were still using some GP9s for yard switchers and I believe a couple are still in use. Also a few years back they were still running FP7s. Sadly they were retired a few years back and a few weeks ago they went to the scrap yard.
I actually have a large number of photos of ONR locomotives an equipement. I was modeling the ONR at one time but have since switched to modeling CNR steam in the late 1950s. I still have a couple of Athearn SD40-2s that are in the middle of a rebuild into ONR units. They are receiving new Cannon & Company fans, grills, cabs as well as a host of other detail parts. Sadly they have been of my work bench for a year now but someday they will get finished.
Lately I have been taking a lot more ONR pictures as one of the main ONR customers is on strike and the railroad is losing a million dollars a day in revenue. Seeing as it is a small regional railroad owned by the province of Ontario it is a big lose for them which has resulted in layoffs and rumors of another possible sale to the Canadian National.
Wayne R