Emails and voicemails are absolutely confidential in the US. Revealing their content to anyone without client's consent is a violation of confidentiality.

That said, this particular situation is a little different if the therapist and the facilitator are colleagues. Confidentiality here may not apply if they both say that their interaction was a "peer consultation".

Oftentimes, therapists within the same agency exchange information about mutual clients (if the same client attends a group and individual sessions with different therapists) without the client's explicit formal authorization because this goes under "peer consultation" category. I don't agree with this and I believe that it is still a breach of confidentiality because the client should be in charge of what is and isn't shared between two therapists in this situation, but, technically, you can't challenge this legally.

In the US, oftentimes, therapists are under pressure to reveal confidential information about court mandated clients to their parole officers in the form of "progress reports". Legally, they still have to obtain the written consent from the client, but they often don't. It often comes down to the therapist's choice to lose their job vs to comply with their ethical standards.