It will be instructive to find out what went wrong. But having deiced there this week I can tell you that you self position till you are in line with the marking (which they are well past). You then report ready for deicing parking break set. The trucks then come out from each side to the aircraft.
One possibility must be that the captain thought they had finished and moved forward before receiving the clearance on the deicing frequency. I actually briefed my newish copilot of this danger the last time we were there and the fatal accident with the 747.
I find it hard to believe you would willingly try and taxi between two trucks in the photographed position and there would anyway be no reason for them to be there until the aircraft reported ready.
I also remember needing a fair amount of breakout power to get our aircraft moving after deicing as it was all pretty sticky. So I think the most probable scenario is moving before clearance from deicing. It is a seperate frequency so if you told ground on the other frequency you were finished they would not know any better and clear you for taxi. Expensive mistake, it will probably cost in the hundreds of thousands if they need new winglets or worse. But at least nobody was injured thank goodness.