If a federal judge orders an injunction that shuts down BlackBerry email service in the United States, business customers have the option to switch to another wireless email platform. But <A HREF="http://www.eweek.com/article2/0,1895,1932924,00.asp">migrating to another platform won't come cheap,</A> according to two consultancies that have analyzed the costs of such a move. Switching from BlackBerry devices and servers to a competitive platform will cost as much as $844 per client, according to a report to be issued on March 1 by the telecom consulting firm Telwares Communications.