Hello,
One solution would be:
1/ on each route-originating PE, add a standard community to the advertised routes, do it in VRF-EXPORT policy:
## PE-1 example:
set policy-options community std-iam-from-pe1 members 64512:301
set policy-options community rt-cust-vrf members target:64512:3000
set policy-options policy-statement pe1-vrf-export term 1 from <match conditions go here>
set policy-options policy-statement pe1-vrf-export term 1 then community add std-iam-from-pe1
set policy-options policy-statement pe1-vrf-export term 1 then community add rt-cust-vrf
set policy-options policy-statement pe1-3vrf-export term 1 then accept
set routing-instances CUST-VRF vrf-export pe1-vrf-export
2/ on each route-receiving PE, match on the community && increase Local Preference, do it in VRF-IMPORT policy
## PE-3 example
set policy-options community iam-from-pe1 members [ 64512:301 target:64512:3000 ]
set policy-options community iam-from-pe2 members [ 64512:302 target:64512:3000 ]
set policy-options policy-statement pe3-vrf-import term 1 from community iam-from-pe1
set policy-options policy-statement pe3-vrf-import term 1 then local-preference 200
set policy-options policy-statement pe3-3vrf-import term 1 then accept
set policy-options policy-statement pe3-vrf-import term 2 then community iam-from-pe2
set policy-options policy-statement pe3-3vrf-import term 2 then accept
set routing-instances CUST-VRF vrf-import pe3-vrf-import
HTH
Thx
Alex