As per my understanding you dont do BGP between edges, it breaks the whole concept.
BGP is run between VeloCloud Edges and Physical Devices like Routers. Basically for underlay traffic. For traffic between the edges, VeloCloud use a proprietary protocol called VCRP. This protocol is use to exchange routes between different edges over the overlay. VeloCloud Controllers acts as Route Reflector.
For the ebgp multi-hop, currently it is not supported but will be available soon.