Well, if the players were hanging around, and said "I want to go find the Lich-King. Who's with me?" "Word. Let's go." That would be player choice.
But if the DM, who has the module "Return to Railroad Mountain", decides that no matter where they go to find the Lich-King, they come across Railroad Mountain - you get my point.
(Which I see is just me misunderstanding you. You're talking about how to best get the players to where they want to go, rather than run "Return to Railroad Mountain".)
Yeah, this is a problem. Or it is for me. As a player, I don't want to be railroaded, but usually it's "Ticket, please" when I show up for the first game. Either get on board or walk.
When I'm DM, I have no idea how to get the players to drive the plot. We all want some exciting scenes, but how do we get them? So we all end up sitting around, with me asking "What do you guys want to do?" and then I end up making a plot to get things moving.
More's the pity.