Since this document describes something that has already been done, its status should probably be INFORMATIONAL, not EXPERIMENTAL.

  Contains several unused references.

I sent my Discuss issue in an email to the RFC Editor as follows...

Hi,

During IESG review of this draft I raised two issues.

1. Experimental or Informational?

Normally an Experimental I-D would describe an experiment that is to be run. 
In that case, it would include a description of the scope of the experiment, 
how the experiment will be measured, the way that the success of the 
experiment will be judged, and the proposed next steps depending on the 
success or failure of the experiment.

In this case, however, it looks like the experiment has already been run. If 
this is a record of an experiment that is now
concluded, I think that the I-D should be classed as Informational. If the 
experiment is intended to continue, I think a section should be added to 
describe the on-going experiment.

2. Definition of protocol extensions?

Section 1 says...

  This document defines
  extensions to MP-BGP employed to communicate tunnel end-point
  information and establish 4over6 tunnels between dual-stack Provider
  Edge (PE) routers positioned at the edge of the IPv6 backbone
  network.

This is not consistent with the an experiment (or with Experimental status). 
The wording used in the Abstract is subtly different, and better. Would it 
work to replace this text with:

  This document describes experimental
  extensions to MP-BGP employed to communicate tunnel end-point
  information and establish 4over6 tunnels between dual-stack Provider
  Edge (PE) routers positioned at the edge of the IPv6 backbone
  network.