I should think that in the usual practical, pragmatic way they worked, all available resources were pressed into service, and the trains, and in particular the mountain trams, got where closed roads were a problem.
I am sure I have heard of people being taken down from Bungalow this way.
Sadly, in those pre-helicopter days, the only solace for a rider with serious injury was a roving doctor (most Island doctors placed themselves around the course, but there was no communication with them), who, in many recorded instances, could do nothing for his patient. Many died, who now would be rushed to Noble's and be back out later in the week.
With few marshals, it must have been a heart-stopping experience to come across the detritus of a crash, in the road, and see a fellow competitor broken by the side of the course.
Even where there were marshals, they would simply move the body to the grass, cover him up and carry on, with no means to get him away until the racing finished.