Your question is bit confusing, but let me try
1. On a DR you can go to configured directory for the replication from ePO
2. If you have assigned new repository to a set of agent then only agents will get update from new DR.
There is ePO query to check distributed repository utilization.
ePO query tab and search for "Repositories" > Query "Repositories and Percentage Utilization " will be appear and run that query.
Navigate new repository in Site Name and check Number of client events if it is not 0 than that repository is giving updates to machines.
Please let me know if it resolve your query.
Your reply is the easiest and fastest way(at least to me) to see if the repos are providing updates.
Here's a silly question, how about the other way around, how can we confirm on a client if it received the update from the DR, not from master repo.
Thanks a million!
FRom the client you could look at the actual policy that is being applied. If you want to verify which repo it is pulling from you can coonect to the remote agent log and see which one it uses. It will be easy to read and will tell you where it is going to get its info from. You can look at edit auto repository list from virusscan console menu option as well.