Gartner Inc. analyst Todd Kort estimated that as up to a quarter of the nearly 4 million BlackBerry users in the U.S. could be considered government workers eligible for the exemption. But he stressed that Gartner believes there is only a 10 percent chance that a court injunction that shuts down the BlackBerry service will take effect.

RIM argued in its own Jan. 17 filing that exemptions would be complex to implement, but NTP believes the matter is simple. Carriers would shut off service to all BlackBerry users, except for those in government who had contacted the carrier for the exemption, Wallace said.

RIM also wants more than 30 days' notice before any injunction takes effect, but Wallace said RIM has had years to fully comply.

The case is due back in court Feb. 24.