Hi Mik:
Thank you for the photos. My guess is that Hawaiian Railroad took a motorised horse car and modified it to run on rails.
The RGS Inspection Car No 1 was a model T ford similarly equipped. Apparently is was too tippy. Accucraft produced a model of RGS No. 1 .
I guess the Delton and Aristo Car motor cars are inspired from these motorised horse cars.
That Model T bus #16 is visually beautiful. Not so beautiful for the driver sitting out in the cold and the ride I assume would be rough and bone jarring. Strange how in those days the vehicle operator was left outside in the elements while the passengers rode in comfort. Notice the wood slate bench on the roof. No seat belts of course. The passengers had better on to something to not fall off!
I viewed a commedy Disney film featuring a wealthy Banker who was having trouble dealing with his wife campaigning for females to acquire the right to vote. All of the Victorian architectural beauty of the house was displayed in the film. At the end of the film the banker and his family walked out to the street and boarded a horse drawn railbus similar to your last photo but fancier.
Norman