Do you know whether those prohibited recordings would be admissible as evidence in court, despite being non-consensual? Or is the weight of their prohibition that they are inadmissible?
No that's not true. A private person can privately record any conversation he or she wants. (Remember Monica?)
Warrant requirements only apply to government action, meaning the government itself or someone acting on the government's behalf. If you talk to someone on the phone and that person records you on his own, without government inducement, then the court will consider the recording hearsay but admissible at trial under a few exceptions to the hearsay rule.
Do you know whether those prohibited recordings would be admissible as evidence in court, despite being non-consensual? Or is the weight of their prohibition that they are inadmissible?