I just tested it and you are right, it doesn't work if there are redundant corner vertices in the spline. The problem is that RailClone consideres each segment between two corners as an independent spline, resetting the Evenly rule.
It seems that the only solution is to fix the spline, removing the extra vertices. What about applying a "Normalize Spline" modifier ? If you like, post here the scene and we will take a look to it.
Could a possible future update allow for a bit moe flexibility here? For instance, you could select 'true corners' where posts should be placed, but treat the remainder as 'evenly' spaced?
Sure. Once completed the integration with VRay and Mental Ray (already done), our objective is to improve the core of RailClone, adding new and more flexible Construction Rules.