If railroad means an exertion of GM power that is regarded by the players as intrusive (on player decision making), or implausible, and plot means a sequence of events which affect the players that the GM wishes to see occur then, yes, there can definitely be a plotted non-railroaded game.
The GM just has to be careful that his sequence of events doesn't go against what the players want or is jarringly unlikely.
It's really not that hard. About 95% of the time, imo, player action can be reasonably predicted.
For example the GM has a magic weapon with an interesting curse on it, say it slowly turns the bearer into a demon, but is otherwise beneficial, and his plot is that he wants the item to go to a particular player.
Simply make sure that the weapon is of a type that only that player can use, and that rumours about the weapon's location reach the PCs' ears. Presumably it's in a dungeon. The GM has a good grasp of the players' skill level so he sets the dungeon difficulty to be fairly easy but not so easy that it's suspicious. I mean what's difficult about that? It's D&D, snatching magic items is pretty much all the PCs do.
What's that you say? What if the players refuse the dungeon or fail to win the item? Well, that probably won't happen, so the non-railroaded plot will probably occur. And if it doesn't, well there's always the GM's next evil plot.