Probably you are going to have to talk with the F&W people. If the said railroad is passing thru a registered line, I would think that it might be the trappers right, even though it is the RR's property. I know that the RR people, take care of their own beaver problems...SSS..
In re.reading your post, if the snaring was away from the legal rightofway, then only the landowners permission is needed and a resident licence.. Out of curiosity, why would you want to set that close to a rail line ??