Answering my own question, I think (-;

From: sen_ml@eccosys.com
Subject: OpenSSH Priv Sep and Remote Exploit?
Date: Tue, 25 Jun 2002 07:48:18 +0900 (JST)

> As a side note, does anyone know how to check whether privilege
> separation is enabled?

I presume checking whether there's a process that's running as the
sshd user while in the process of establishing a connection is some
evidence that privsep is working.