Permissions Cases

Hello,

I have been looking in to permissions for my CRM and i have come in to some trouble with viewing Case outside businesses units.

I have the below setup;

As you can see Users in Business unit B are unable to see cases owned by Users in business unit A, even tho the Customer/Contact associated with them are in Business unit B.

What I would like is Users in Business Unit B to see cases that are associated with Customer/Contact of a case even if the owner is outside of the business unit.

Any help will be great.

Thanks