Access to Performance Document after Manager Change

Summary:

How can previous Line Manager access the performance document which is still assigned to the previous Line Manager

Content (please ensure you mask any confidential information):

After a cut-off period, we turn off automated Transfer of Performance Document when there is a change in Manager(during the last few months of the Performance cycle). Some managers have only 1 direct report and when they are transferred to another Manager, the previous Line Manager loose access to "My Team" access as well as the Line Manager role is automatically removed.

So how can the previous manager see the Performance Document of the Employee which is in-progress and is still with the Previous Line Manager?