Ok, I did not explain very weel : see that diagram

When trafic is injected in the MPLS network at PE1, using ebgp balance config, it uses both links. However, at MPLS routers, all traffic is sent on only one link. I'd like all links to be used. MPLS.
Setup is done with MP-BGP and the vpnv4/vpnv6 address families. I found mentions of additional-paths and vpn-route cross multipath , but in H3C commware docs, not on HPE ones
AS prepend and local preference are useful to get priority of trzfic, not using several equivalent (same cost) links.