CALEA is not only for voice. Broadband providers are required to be CALEA compliant. Basically they have to be able to delivery data in a specific format to an LEA.

These devices are not (normally?) under LEA control. The service provider would receive a warrant/court order that says "send data for customer XYZ to this CALEA capture IP". Even if the LEA had direct control of the CALEA device it would need the assistance of the SP to know what data is coming from what customer.