Alarming ambition shown by terrorists who were bent on wreaking havoc
The attack in Barcelona was no real surprise, in terms of following a defined path similar to other Isil-inspired attacks. However, what is new is the level of ambition displayed. This wasn't just a man or two men in a white van casually trying to kill as many western tourists as they could.
The mention of another van being used could indicate that another individual or team were acting as a reconnaissance element. Travelling ahead and reporting back over the phone where the police checkpoints were, and what the level of security activity was. They would also have been assessing the area as to how target-rich it was at that time.
In other words, where was the best place to kill as many people as possible. The speculation about whether they had planned to escape afterwards is interesting. Previously such assailants have wanted to confront the security forces, not evade them.