For getting reference to the nested RadListView you will have to first get reference to the parent RadListView control in the edit template of the grid with FindControl() method. Then, you will need to use FindControl() from the parent RadListView items to find the nested RadListView.
Using your grid structure, following is an example for getting the nested RadListView of the first item in the parent RadListView:
Please keep in mind that if you need to find controls within the nested RadListView you will need to use the items from the Items collection of the control.
Hope this helps.
Check out the Telerik Platform - the only platform that combines a rich set of UI tools with powerful cloud services to develop web, hybrid and native mobile apps.