The crossover point isn't exactly anyone point.  Its more of a range, where for each user the calculation is dependent upon their particular circumstances like what generation equipment they have and how efficient it is, what region they are in, whether they have any long term commitments to coal, whether producing power from coal is profitable at all (for those producers that don't have the ability to generate with NG), etc.  So as NG rallies, we would expect to see less NG usage and more coal usage, but it wouldn't necessarily happen all at one price.