Stansted Express
The Stansted Express is going from every 30 mins to every 15 mins as part of the new franchise. But at £13.40 each way, how do they need any more subsidies?
Putting money at Heathrow towards Crossrail is much more justified + EDI & GLA are both valid candidates for rail extensions (think EDI is getting underway).
I would send your question to BAA, and let us know the response. There is certainly no point if it just goes on empty buses running around with no passengers. This happened as part of the "public transport commitment" at Warwick Parkway station