We recommend that you install the system such that NT authorization/security is used, not hard coded SA password access (which is not as secure - this is the same recommendation MS gives). The account associated with the local Unity services (in particular AvCsMgr) should be a member of the local admins group (or the builtin group if it's a DC) and that group will, by default, have RW access to the UnityDB and ReportDB databases in SQL.
Assuming the folks followed these instructions for their Unity install then you shouldn't have to worry about this.