[dredmorbius]

If the system used SMS proxied by TextSecure, that would have at least avoided net-of-endpoint pen trace. You'd know who TextSecure's customers were, and could probably use time-based analysis to see who is likely to be talking to whom (a steady stream of non-content messages would otherwise have to be used to mask significant messages).

The context analysis sideband leakage is the big win here for a data-based approach.