Is there any documentation that covers this subject that I can make available to the customer?

I belive you will have a problem with the phisycal DM, because no matter in wich domain is the CIFS created for CAVA, it will see ALL the filesystems of all the VDM mounted in that DM (server_x). So to me understanding the only way to separate it for different Tenant is to use a different DM for each Tenant.

That means that depending on the VNX model you will have a limit from 1 to 8 DM or separated Tenanat.

I think you have to bring AV services as the Infrastructure owner to all tenancys. So put a CIFS in the management network with 2 or more AV server in the management network to serve all tenats.

I think I'm getting closer  the customers main concern:

Can someone help me address this concern?

I am basing my information on the configuration guide that has the details listed below. This implies that CAVA will scan through a CIFS on the physical data mover…. My actual concern is that permissions for the VDM will be assigned based on the customers active directory environment (CAVA server in the customer environment cannot talk to the physical DM located in the management network and a CAVA server in the management network cannot talk to the domain in the customer network.

CAVA and Data Mover On VNX,

you can configure a CIFS server on a Physical Data Mover or on a VDM. Typically, the CIFS servers are configured under a VDM (one or more VDM on a physical Data Mover). However, for the CAVA to work, you need to have a CIFS server configured on the physical Data Mover against which the virus checking will be done and the userrights or permissions need to be assigned against this CIFS server. This is the global CIFS server or the default CIFS server on the Physical Data Mover. Note: All file systems or shares can be mounted under a VDM. However, CAVA will scan all the file systems under the Physical Data Mover covering all VDMs and all CIFS servers.