I'm going to say no due to this
For the People Rules wrote:
5.81 INTERCEPTION PROCEDURE: Any force with a general (not a general alone) may attempt interception. An interception can occur whenever an active enemy force enters an adjacent road/rail connected space that does not contain an enemy SP or fort.
It does not say river connected in 5.81. I think 6.52 is a specific exception to 5.81 that the Union has the capability to execute due to their phenomenal cosmic power over waterways.