By that standard, nobody has any right to anything. I think it's pretty widely understood that rights range from aspirational descriptions of a just world to widely accepted legal consensus.

That the state which grants you your right can take them away doesn't make them flimsy.

And it's certainly more than "hardly" a monopoly. If the government gives a certain company right to operate on train track infrastructure but denies the same to every other company, then does that first company hardly have a monopoly?

Sure. That’s how rights work. It’s why we need to keep on fighting for them when necessary.