Several things have happened recently. First, there's a surplus of single-hull tankers in the world, and that has driven down the cost of potentially shipping raw water. In most jurisdictions you would only need single-hull tankers, so that perhaps has lowered the cost. On the other hand, desalination costs are dropping very rapidly, so potentially, in some jurisdictions, especially the Middle East and farther south, the idea of moving fresh water is bumping up against the costs of desalination. Technology changes could move in both directions, making it more or less feasible.
The available evidence right now, though—and it's in fact provided by the policy research initiative of the federal government—indicates that the costs are prohibitive. They are in the order of, for the types of scenarios they looked at, $8 to $15 per cubic metre. When you translate that into the values that are paid right now in the areas where water would be sent, it's simply that there'd be lots of other suppliers of water, if you were to try to get that price in those areas. It's just not commercially viable, and the orders of magnitude suggest it's not going to be in the foreseeable future.