Is it a tax? Is it not just trying allocate the fare revenue to Tfl/non TFL services in a fairer way. I suppose the fares could be all the same with transfer payments being made between TfL and Dft/TOCs to make up the difference. I'm not sure the appropriate tax payers would be happy about that.
The term tax is just a colloquialism, but if walks like a duck and quacks like a duck...
Take a journey like Plumstead to Liverpool Street. You pay more for that than you do from either Abbey Wood or Woolwich, because you're charged a mixed mode fare. So not only are you inconvenienced by having to change, but you're charged extra for the privilege.
Obviously having this mixed mode generates extra revenue but it's rather iniquitous and does little to enhance the attractiveness of public transport.
BAA built the Heathrow tunnels didn't they? Why shouldn't they make money of the use of their private assets? I'm sure they would be happy to sell them to NR/State for an appropriate price. Or do you support the expropriation of private property?
It was initially a joint BAA-BR project. BAA later bought out BR's 20% stake.
The point isn't necessarily that it should become expropriated (what's done is done), but rather that BAA shouldn't be allowed to charge disproportionate track access charges, which is what at the root of the Heathrow "tax".
Yes, of course, building a tunnel is always more expensive than a bit of plain line. But the charges are utterly ridiculous and allow BAA to make a disproportionate profit on a piece of important national infrastructure.