The UK rail service is obsessive about fencing.
The majority of railtrack that I've been next to throughout Europe and the USA has been unfenced. Seems like folk there don't need to kept off the tracks.
Animals on the line.I nearly hit a deer when I was doing 80mph.One of our drivers hit three sheep when he was doing 100mph and I've seen animals and people on the track at various times and places.When railtrack get a report they generally look round for the problem and fix the fencing or fence it up.Actually I've had a few nasty ones.Plus we don't want animals and people on the line when there is third rail 750 volts around or high linespeeds,overhead wires.