Communication to an Auditor...

Well, good question. I would also like to be updated on this matter.

not at all. The outgoing Auditor Can't be expected to conceal such information. it is evident from the legal requirement that ,

The Incoming  auditor is required (Under Schedule 1, Part !, Clause 8) of the CA Regulation Act to ask the outgoing auditor of Any Reasons why not to take up the audit. It is therefore the duty of the outgoing auditor to inform the new auditor about any significant area of concern.

This position is also specifically excluded from the auditor's duty of confidentiallity as imposed by AAS 1

AN AUDITOR IS NOT ALLOWED TO DISCLOSE INFORMATIONS OF HIS CLIENT'S BUSINESS EXCEPT WITH THE PERMISSION OF CLIENT OR WHERE LAW REQUIRED TO DISCLOSE SUCH INFORMATION. BUT, HE IS NEITHER REQUIRED NOR RESTRICTED TO DISCLOSE ABOUT FRAUDULENT ACTIVITIES OF HIS CLIENT'S BUSINESS TO THE INCOMING AUDITORS. IF EXISTING AUDITOR RESIGNS DUE TO SUCH FRAUDULENT ACTIVITIES, HE MUST INFORM  THE REASONS THEREOF TO THE INCOMING AUDITOR.