Negotiating the Business Liaison Interpreter's role Boundaries

I am getting deeper into "Community Language Interpreting - A Workbook". This a practical book. It does not dive deep into theoretical considerations, but it does raise without discussing further issues of major interest, issues I have not seen developed elsewhere as well. I am referring here to page 52 and the brief explanation of the scope of work and contexts where business interpreting may take place. I am more especially interested with the sentence starting with "Business interpreting is different from community interpreting ....". You can read the page and more over GoogleBooks here although I would strongly suggest you purchase the book and in doing so, support further development of content geared at community interpreting at large. Free ad pitch ends here. The crucial sentence is this one :

"In the case of freelance interpreting, the interpreter's role boundaries have to be negotiated beforehand. Sometimes interpreters are expected to play the role of an agent or a delegate member, so the interpreter needs to clearly determine the boundaries beforehand to avoid disappointment and miscommunication and to curb the ever-present risk that the failure of negotiations or business meetings may be blamed on interpreters."

If I had colleagues in front of me ready to discuss this matter, I would ask them right away : "Do you have a standard discourse to your client explaining your role, the extend of it and the alternative positions an services you may provide or not"? My own answer to this question is negative. I don't have a formated ready to read aloud, and it does feel that something in the line of a formal discourse is in demand. Legal interpreters must sign and pledge an oath. Business interpreters may need to think and act in terms of warning clients prior to delivery.