incarico fiduciario

05:48 Feb 5, 2018 

Yes "confidential" would not apply not the definition you have just given, but evidently that was not the definition the asker wanted - but rather that of an employee beholden to secrecy. In this case it is common to use the term "confidential" to refer to this type of employment.
As far as I know, the term "incarico fiduciario" is not established, contractual jargon but rather a term coined by the person who drew up the contract, ergo I interpret "fiduciario" as simply an adjective. I could have used the direct translation "fiduciary", but that would have created ambiguity with its usual meaning (akin to "trustee"). I presume the asker had this final dilemma, otherwise she would not have asked the question since the translation would be straightforward.

05:09 Feb 5, 2018 

The fiduciary duty of a surveyor to his/her client is the duty of compliance with professional ethics to the benefit of the client, including (presumably) the duty of requisite accuracy, and the duty of following the client's instructions to the extent feasible. In this context, the concept of "confidential" might be excessively narrow, or might not apply at all. E.g. suppose the surveyor was engaged to settle a boundary dispute between the client and another party (as is often the case). Confidentiality ordinarily would in no way apply to the situation.