Also, the change should be to move away from Microsoft Office in favor of tools suited for the tasks at hand (databases, project-management applications, bug trackers, requirement management tools...) and only migrate to GSuite for the subset of tasks where having an office suite makes sense.
The biggest challenge (as I saw it) was making sure that everyone could email everyone else all through the transition because if email stops, the company stops in that portion.
All of that to say that even though Airbus is one less than a third that many employees (133K vs 450k) its organization complexity is up there. And keeping complex organizations functional and efficient as possible during a large transition is often addressed by keeping the rate of change manageable (aka slower than you would expect).
That said, the other commenter is also accurate: a "full" roll-out will not mean 100% replacement. Things would break and it would be an irresponsible management decision to force some things that shouldn't be forced.
Source: I led a large MSO-->G Suite migration in a previous role.