No, VM's phone service from the hub is simply a voice connection (not data) so the pod RJ45 is no use.
If you already have a cordless phone, you could buy another satellite handset to match the first (or one from a different brand that is GAP compatible assuming your existing base is GAP compatible too). A GAP compatible handset from another brand would only work with basic phone functions though and may not be that reliable.
Alternatively find another satellite charger base for the existing phone (from eBay etc.) and leave the existing phone charging downstairs with the existing setup.
If you don't wish to spend any money on new equipment and don't wish to (can't) move the hub then you need VM to rewire your phone socket so it links to the hub's phone socket on the back of the hub.
That may involve some wiring to create a link from the hub to the existing phone wiring. If you happen to have an existing phone socket next to the hub position it should be simple. If not some telephone wiring will be involved.
A VM person should reply within a few days to discuss/arrange. I think they often do the switchover first and then arrange phone wiring after the switch is complete.