Just curious as to exactly what this pump will be supplying?
Pumping water on a fire supplied by propane likely does little to extinguish the fire, unless you really get some massive volume of water in relation to the available fuel.
Now after an incident in the area in recent years, where a fire developed and was burning leaking fuel at the base of the tank out of a damaged or malfunctioning pipeline fitting/component, the growing concern at this scene was how much more heat the tank would be able to take before the tank itself was weakened enough to cause a major event to happen. There was pretty much no chance of putting the fire out - the fuel needed to be cut off. After this thing burned for at least 3 or 4 hours firefighters finally sent one man in to shut off a supply valve and gave him a pretty heavy shower of water while performing that task. Once the valve was closed the incident was essentially over. They had been working on evacuation of a large area of that city because they were not sure just how big of an explosion may occur if that tank wall failed, later investigation did reveal that the tank wall was compromised and needed repairs.
Now that I got that out of the way - A fire pump supplied by utility power still needs a service disconnecting means supplied by either a separate service or tapped to the supply side of the other service disconnecting means and it can not be in the same cabinet, enclosure or vertical switchboard section as the regular service disconnecting means - chances are it will be integral to the fire pump controller in many cases though. It would still need to be isolated from the regular facility service disconnecting means just like it would need to be inside a building - the idea is to minimize the possibility of accidentally turning off the fire pump disconnect when disconnecting the regular power service disconnecting means.
It can come directly from the transformer, you have many possibilities of how to support it, and the physical size of the controller will have some impact on how that may be done. Not sure about why you mention the 12 inch clearance from the bottom, it could be an installation instruction to specific units, but I don't think is a code requirement otherwise.
