http://www.news1130.com/2014/04/12/still...ng-pattullo-as-surrey-new-west-disagree/
"Surrey Councillor Tom Gill says New Westminster understands there is pressure from a regional position, but New West still won’t agree to a six-lane replacement crossing – even if one lane remains closed - until infrastructure upgrades catch up.
“The context of a six lane bridge was simply that until infrastructure materializes on the New Westminster side in terms of possibly a tunnel or other infrastructure improvements, that third lane not open. Again, New Westminster was not open to that dialogue.”
==============
New Westminster is clearly not worried about an underused bridge if they are demanding a tunnel to go with it.
6 lanes is not only about capacity, it's about safety (not having slower trucks merging at the bridgehead) and not having police incidents paralyze the region for 4-8 hours.
The extra lane on the Surrey side would serve the same purpose as the climbing lane on the "cut" in North Vancouver.
New West should be stating explicitly what form and alignment they would want for their tunnel. It might be one thing they and Surrey could agree on.