Thanks for that gg. I forgot about the traverser. So, the loco pulls the train in, uncouples, goes on the traverser, the loco runs around and pushes the train in one wagon at a time. Then collects one wagon from the traverser one at a time and adds it to back on to the train as it pushes the loaded ones in.
On the note of splitting freight trains. I believe the new terminal built for the IWT requires it to be split for loading and unloading. Again due to space reasons a the docks.