This is more a business issue than a tech issue. There are two dominant RTI systems providers in England (where my bus knowledge comes from), and only a few more in the world. If they start providing an open data feed of real time locations, then they are giving a leg up to competitors who would potentially be able to leapfrog their predictions, as well as undercut them on price. This would threaten their ticket machine business (the ticket machines incorporate the GPS tracker - something like 98% of buses in England have GPS). Having spoken to all of the RTI suppliers during my work for DfT in the UK government, I am convinced that they will not release these data unless legislation forces them to.

And that is basically what is happening early next year.