[j-nsp] mpls-relay and pim

[hjan]

I have some trouble with pim over l2 tunnel built with mpls-relay.
In a scenario like this:

CISCO PE --- E320 --- DSLAM --- cpe

with mpls relay enabled on e320 pim neighborship between cpe and pe
didn't come up. All the rest work fine, bgp comes up, ping works ecc.ecc.

Below the conf of the juniper interface:
interface gigabitEthernet 2/0/4.3100
!
 vlan id 3100
 mpls-relay 10.255.255.255 3100

any hints ?

Regards,
Gianluca