I know I'm not supposed to, but I love new railway lines, no matter how much money is wasted on them. Ain't nothing like a train.But why is Brian "not supposed to" like trains? Perhaps it's the "wasting" of money, lots of which is extracted from the taxpayer. Many libertarians and conservatives dislike railways precisely because of the almost universal state involvement. In a fully libertarian society, though, it may well turn out that railways would be more successful and roads less so. We can't tell in advance. For the sake of argument let's assume that railways need state subsidies.
I recall reading somewhere that the great Austrian economist Ludwig von Mises favoured privatising virtually everything but made a rare exception for the Vienna Opera House. Mises was an opera fan. If the great Mises can be granted his subsidised opera house perhaps we can allow Brian to enjoy new railways, no matter how they are financed.
Let us assume that we have achieved a society in which the only function of government is the protection of citizens from aggressors. Which single exception would you choose to be subsidised?