The Federal Rail Administration assigns every section of track etc. a number called FRANODEID. If you took US rail network data from FRA/BTS and adapted this tool to use it, then you could route that can from any line in any yard to any other. I think these numbers are the 6 digit numbers in the waybill posted in the other comment.
In the example I posted, in the F9 and D9 lines, the first number is the FSAC (freight station accounting code), the second number is the SPLC (standard point location code - different from what you're referring to), and the last number is a Canadian-style postal code.
