Well the problem comes down to what is considered "unreasonable searches". When I think "surveillance", I think cameras on cars that photograph everything they pass by. The courts have again and again considered those to be reasonable with no expectations of privacy. And the trucks in this article are doing exactly that.
Uhh FalcoNet doesn't photograph cars. It snoops telecom traffic. And no, SCOTUS has certainly not found that the government is allowed to just arbitrarily snoop telecom traffic.