In my opinion I wouldn't think it would be covered under warranty as it is an adjustment..... you could possibly have hit a pothole and put the alignment out, so would not be classed as a manufacturing defect.
I suppose it would depend how long you have owned the car, if for example you had just bought the car then they may cover it, but if you have owned the car for months then I wouldn't expect it to be covered.
I doubt that it would be covered as it is classed as wear and tear. With the state of the roads it is so easy to get the tracking knocked out of alignment. You are best shopping around for your tracking as most tyre fitting centres carry out that type of work (and cheaper than you have been quoted by the dealer).