Haven't tested yet, but I assume following article is helpful;
How to route leake between vpn instances configuration example / https://community.hpe.com/t5/Comware-Based/How-to-route-leake-between-vpn-instances-configuration-example/td-p/6968623#.XAU8RtvwaHs
i.e.
Prefix-list for the networks you want to leake.
ip prefix-list v001 index 30 deny 10.50.25.248 30 BGP Peer
ip prefix-list v001 index 40 permit 10.50.24.0 24 Leake network
Route-Policy
route-policy v001-export permit node 10
if-match ip address prefix-list v001
apply extcommunity rt 1:1
VPN-Instance configuration.
ip vpn-instance v001
route-distinguisher 64514:1
import route-policy v136-export
vpn-target 64514:1 1:136 import-extcommunity
vpn-target 1:1 export-extcommunity