Can you use a pipeline 7 feet in diameter, 2 miles long, moves at 50MPH, and can go to any major refinery west of the Mississippi? That is what your average UP train can do. I work for the UP, and barring the oil companies being banned from building pipelines, we’re the second choice for moving crude. We despise buffett and his toy train set. Until we can get these pipelines built (which by the way, UP moves a lot of material and supplies to the oil patch), trains are the closest thing to a land based oil freighter.
The space between cars reduces that to about five feet. A minimum headway of about ten minutes (tight for a heavy freight train) reduces the effective speed by about two thirds. When one throws in the headway for the rest of the freight that must be accommodated on the line (especially all those empty containers going to Western ports and hoppers carrying coal) I'd cut that number at least by half. So your analogy is more representative at a five foot tube moving eight miles per hour, which isn't much different than a pipeline. Yet the place where that number really drops is in transits through urban areas, switch yards, and loading/unloading for distribution into a refinery. Hence, all other costs not taken under consideration, I would doubt that a train system could move oil as fast as a pipeline. I also wonder how many refineries have the yard capacity and unloading facilities to handle that many tank cars as fast as they might otherwise arrive.