Honestly, I think this story probably would have worked better if it was set in a transitional period when motorized fire engines were just starting to become widely adopted such as the late 1900s or early 1910s as the Springfield Fire Department (according to Wikipedia) was the first municipal fire department in the United States to completely motorize in 1913. Where this short fails for me is that we clearly do see modern cars (for the time). So, why would a municipal fire department still use a horse drawn one when just about every single fire department in the United States would have definitely been motorized by the 1920s (for the most part because even rural departments had already been looking to buy their own)? Unless the fire chief is just that stubborn. And even then, it is hard to believe.
Now, if it were set in a transitional time period, you can have the horse drawn engine and the motorized fire engine compete to see which one is better. Fire Chief Kelly’s character will also make more sense because he will be from the old school days of firefighting and not quite understand what makes these new fandangle contraptions better. Maybe the motorized engine can have a few mechanical problems that side line it which initially prove his point but when it works or once the teething problems get sorted out, it is easily more efficient than the horse drawn one. Kelly could even be forced to use the motorized one to his chagrin. I must say, I love horses a lot. But when it comes to emergencies, I would prefer a self-propelled fire engine be the one responding rather than a horse drawn one because when I am in desperate need of help, I want it to come sooner rather than later.