I have called Union Pacific in the past and they will have the answers you are looking for. Give them the location and they will be happy to assist you.
UP Main Number: 402-544-5000
UP Operator: 888-870-8777
Hope this helps,
The more time it takes to get your answer the higher the probability that someone else may actually make an offer on this property.
The fastest way to get your answer is by driving to the neighborhood and knocking on a few doors. You can ask specifically about the repetition of the train schedule and also obtain a better understanding of who lives in the neighborhood and how friendly they are.
Regarding the train schedule, be sure to ask about the schedule now and how it has changed over the last 3 years. With the economy in its current condition fewer goods are being shipped, so expect that shipments will increase as the economy improves.
But the answer you've gotten is pretty normal, really. I live near a town with tracks running through it. And, really, unless you're within a block or two (and sometimes even then), you really do get used to it. Where I am, and where the track is (in Northern Virginia), the track serves freight trains, Amtrak, AND a local rail commuter line (VRE). If I had to guess, I'd say trains probably average once an hour . . . but, really, you get so used to it, it's not an issue.
Meanwhile, where I work is about 300 yards from a power plant (in Alexandria, Virginia). There's a rail line about 100 feet from my window, and trains are going back and forth all the time delivering coal to the plant. In fact, looking out right now, there's a Norfolk Southern train (locomotive number 3536 for all you train buffs) just parked there. Honesty, you get used to it.
One thing you should do is look at the comps for other properties about the same distance from the rail lines as yours. That'll give you some indication of how much the tracks/trains are affecting property values and thus "if this property is worth buying." And, again, do ask the neighbors.
Hope that helps.