The government pays the train operating companies to operate trains, not to feed data to iPhone apps, just as they're not paid to sell crisps and sodas from a small cart. This creates value (otherwise there would be no profit to extract), so why not?
The government pays the train companies to run a transport service; departure times are an essential part of that, in a way that crisps quite plainly (or quite saltedly, ha ha ha* ) are not.
I agree that large-scale API provision is added value, and I have no objection to a private company making a profit from that. What I object to is a private company being handed a monopoly on that private data, with no effective oversight being given to the terms under which they provide access to it.
ATOC, by dint of the exclusive licence granted to them by Network Rail, have complete control of the market for this publically-funded data. They are adding value by serving it as a reliable API, certainly; however the price they are able to command has little relation to that value, because they have no competitors.
