The more I look at it, it looks like there may have been only one lane blocked initially and when the info was posted on the sign. The officer is the only one blocking the second lane, not the trucks with the safety lights. It's possible that the officer needed to block that second lane so an emergency vehicle could get in place or something.
To me, the biggest thing I see is that those signs are just a warning and should never be taken as an exact description of the situation. They should probably modify the policy to not give any info on which and how many lanes are blocked. I know it seems like useful information for motorists trying to get through but... look what happened. Police are always modifying the amount of traffic that they need to divert. Shoot, they could have had 3 lanes blocked if they thought they needed to.
Also, I just can't help but think that he was going way too fast for that environment. If there was nowhere to go to his left, that tells me there was a lot of traffic and you KNOW those lanes on his left weren't going very fast. I also know that a big heavy coach like that is not going to stop as quickly as mine but still....
I know I'm not an expert but my gut feeling is that he saw all the slow, backed up traffic in the left 2 lanes and since the sign said only one lane blocked, he figured he would just cruise along in the lane he was in. Once again, happy in the information he wanted to hear, he probably didn't slow down anywhere near as much as he should have. Also, he probably wasn't the only one. Unfortunately, he was the one in the huge vehicle that doesn't slow or maneuver well.
I think that he did screw up. I think there were things he could have done and they were all before he pooped his pants and tried to thread the needle between that cop car and the road safety truck. He has to protect himself and his wife so he needs to say what he needs to say....