Even if the property line fails to extend to the center of the railroad tracks, easements or rights of way across railroad tracks are very common. Railroad crossings are easements to the railroad property (whether implied, prescriptive or otherwise). So you're pretty much on the money: a railroad crossing easement can extend not only to the center of the railroad it can extend across it entirely. I suspect they will view the bike path easement and the crossing easement as two separate types of easement or separate easements. But nonetheless: easements. A railway propery tract (easement) can extend some 10' to 20' or more feet on either side of the track.
Attachment 4743
re: The Rock Island System
Likely you won't be surprised (1) that I bothered to look or (2) at what I found:
1. City of Colorado Springs was established *AFTER* the Civil War
2. the entities owning the Rock Island system were formed *BEFORE* the Civil War (see Wikipedia)
The Rock Island rail system as of 1965
Related
Landlocked by Railroad