We always involve the customer in our mock recalls and one of our steps is for the customer to confirm the number of units received.
The reasons for us doing this are:
1. The Sales team responsible for customer contact with us are involved in the Recall trial and it maintains awareness in that dept. of what would be required in a real recall scenario.
2. The customer involvement means that we have verification of what we actually despatched, exact number of units, etc.
3. The customer involvement means that they get experience of our Recall procedures and can feedback any comments.
4. Customers and external auditors have a greater sense of assurance that our recall procedures are in place and are being trialled as realistically as possible.
In a nutshell, I don't see that you can really do a trial of your recall procedures without trialling the communications with your customer(s) as part of it?
There are also downsides to this, of course.
1. Weaknesses and mistakes might be visible to your customer.
2. Customers aren't always motivated to participate in a timely manner and communicate back their information.