I was thinking that myself. There's not much grass between the rails or ties.
I think, based on a close look at the picture, that the contraption with the reel mowers is designed to mow between the rails. (??)
My experience with reel mowers is that they will not mow any grass or weeds that are more than a few inches tall. The blades of grass get pushed away from the bedknife by the reel if they are too long.
So this thing must have been for someplace where they wanted a nice lawn around the rails?
Does that make any sense?
On a serious note, I think trimming the ROW has become too big of a job for 4-5 personal sized string trimmers, especially with the heat we've had this summer. It's tough work to go at it all day.
A solution may be some sort of clever mechanical device, kind of like Joe Lindsay.