As for the background check regarding a "railfan's pass," don't you think railroads, law enforcement, or since you mentioned the NRHS as a requirement of this pass, historical societies have more important things to do than this? Trust me, besides the risk of terrorism, there's another reason this wouldn't fly:
Railroads don't want you on their property because of severe risk of injury and or death to you or others. Don't tell me that some won't think this pass would give them access to everything, including private property.
And if you think just cause you're a railfan that you know more than the average Joe, read on...this from the Railpace Hotnews page:
BE CAREFUL WHEN PHOTOGRAPHING TRAINS!: A Pennsylvania man was killed Thursday in Savannah, Wayne County, when he was hit by a car as he attempted to cross a bridge over railroad tracks. Ian Purkiss, 59, of Williamsport, Pa., was struck and killed by a vehicle around 3:52 p.m. while he was photographing trains, police reported. A vehicle traveling south on Hogback Road struck Purkiss who was transported to Newark Wayne Hospital where he was pronounced dead. State Police in Canandaigua are attempting to reconstruct the accident at the scene. Ian Purkiss was a longtime active member of the Central Pa. NRHS. He was a contributor of news photos to Railpace as well. He will be missed! The investigation is ongoing. (Joe Calisi, Sandy Mitchell - posted 4/09)
Now I know, someone will get smart and say he was hit by a car...not a train. Don't think that's ever happened? It has. And I'm sure the railroad has had to deal with lawsuits from the "victim's" family. For that reason alone, don't expect a pass to trespass.
Jay