There was a while when all of the X-Men were immune to electronic detection. They had decided to stay 'underground' after they were presumed dead. I assume this is shortly after that.
Incidentally, there's a great scene of Colossus fighting one of the Brood in the middle of Dallas (I think) with a TV cameraman filming it. He's calling in the action, but the people in the studio can't see Colossus.