I just had this same question. In our case running a DR4100 backup appliance with CIFS shares. No way to limit CIFS container/share on the DR4100 I don't believe, so was hoping to be able to do it from within Veeam similar to how you can with CloudConnect quotas, but set at the repository level.
Relevant in our case for hosted clients on our infrastructure (a number in same datacenter) where we don't use CloudConnect, but still want a way to limit and account for their storage usage on the DR4100.
Hope the above makes sense.