There seems to be a small bug, connected to Server 6 and Power Stations in particular, where the coverage area of the railway station doesn't coincide with the area on the map. This means that you can place a railway station so that its coverage area just covers part of a power station, but the power station won't accept coal. I have only noticed this happening at the right hand side of power stations on server 6.
There was something very similar with oil refineries on the Hard Server a couple of years ago, but it has been fixed.