Interesting question. My own feeling is that NYC would avoid using the CASO as a route for reefer traffic just because of customs problems. You can bring a lot of things across the border but just try an apple or an orange...big no no. Delays at border crossings with time sensitive ice and perishables just doesn't work very well. Perhaps if they were sealed tight and all the paperwork and brokers lined up beforehand without a fault, but still I question it. Bugs, mould, various organic plant diseases and so on are really controlled.
I have seen many pictures of NYC trains on the CASO and personally witnessed many in my day but do not recall reefer traffic.
Having said all that there is a great deal of agricultural traffic flow between the 2 countries. We get tons of stuff from California and I know that Ontario fruit is considered somewhat gourmet on the Eastern Seaboard so what the heck do I know.
The Canada Southern.com website has so much info it would take you a year to get through it. There are consists from the late 40's, the 50's and early '60's during certain periods of time and tons of pictures. Very detailed passenger consists with car numbers and type, loco # and type, engineer, conductor names. Even the number of passengers carried on a particular train that day or night and how many Pullman beds were sold. Lots of mail and express trains and seeing the steam to Diesel transition period is fascinating.