If the FBI was at all smart, they would have installed call-home software on those laptops and probably have a majority of them back right now....
For those that don't know, call-home software is a way to stop laptop theft. Once activated, if the laptop modem is plugged into a wall jack, it calls a home office of a security office and lets them know where it is to within 100 metres (possibly ANY net connection now, even high-speed). So basically, if you steal one of these laptops, you can't use it for the net.
And no, formatting won't work. I believe on some of them it is etched into a chip... can't quite remember the exact details, but its basically impossible to remove it (changing HDs won't work either)
But again, never give the government credit for doing something smart... I mean, that protection could cost them valueble money that they can be using to give themselves raises!!