I am facing the same problem as below posting.
I had 2 X STM-1 connection from PE2 to P2. The TE explicit path that defined the next-hop address to P2 is the loopback IP of the P2 router (not the physical SMT-1 IP), therfore the loopback IP of P2 is equal cost from the OSPF prespective. So I belived it can be load balance between 2 STM-1 links.
But when I send the traffic down to the tunnel, it seem like traffic when to one of the STM-1 link.
See attached diagram and the PE2 configuration and some show mpls screen shoot.
p/s: the PE2 is running IOS XR.