Basically there are two types of load balancing for VPNV4 routes 1) Equal cost 2) Unequal cost
Equal cost load balancing for VPNV4 is the same as IPV4 load balancing
Equal cost load balancing cannot load balance VPNV4 routes received from different igp metrics and different cluster list length , which I beleive is your requirement .
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Protocol-independent load balancing is applied to VPN routes that are equal up to their router identifiers (router-id) with regard to route selection/
This is the default load balancer for vpnv4 routes (i.e equal cost load balancer), which is the same as ipv4 load balancing in which load balancing occurs if untill router-id ,other attributes before that having same cost. .
This is the default behavior , if unequal-cost knob is not configured.
With Unequal cost knob enabled my last mentioned Post explanation holds good.