CloudMirror doesn't provide an example of IStorageProviderCopyHook implementation

The documentation for CloudMirror was updated to reflect the support of IStorageProviderCopyHook interface by cloud files API. The interface is not documented.
I tried to implement it without success. Only the constructor and destructor of the custom implementation are getting called, but not the CopyCallback method. Example code:

#include "stdafx.h"
#include "StorageProviderCopyHook.h"

StorageProviderCopyHook::StorageProviderCopyHook()
{
    wprintf(L"StorageProviderCopyHook constructor called\n");
}

StorageProviderCopyHook::~StorageProviderCopyHook()
{
    wprintf(L"StorageProviderCopyHook destructor called\n");
}

IFACEMETHODIMP StorageProviderCopyHook::CopyCallback(_In_ HWND hwnd, _In_ UINT operation, _In_ UINT flags, _In_ LPCWSTR srcFile, _In_ DWORD srcAttribs, _In_ LPCWSTR destFile, _In_ DWORD destAttribs, _Out_ UINT* result)
{
    wprintf(L"StorageProviderCopyHook CopyCallback called\n");
    return E_NOTIMPL;
}

Produces next output on file renaming:

StorageProviderCopyHook constructor called
StorageProviderCopyHook destructor called
Thumbnail requested for....

So, CopyCallback never gets called. Please, provide an example of working IStorageProviderCopyHook implementation in the CloudMirror sample.

Start by inspecting the CloudMirror sample and its StorageProviderCopyHook.h implementation, then trace how the IStorageProviderCopyHook object is registered and invoked. Use the reported rename scenario to verify that CopyCallback is reached and that the sample contains a working implementation example.