It will open all at once as far as I know. Doesn’t make a ton of sense in the grand schemes of things to open it in phases. Also if they did do it I believe the Epcot to CBR line would be the last to open not Pop.I wonder if they will open the entire system all at once, or branch by branch? If branch by branch, they could start operation with a partial cabin delivery.
Advantage to doing this is:
1. Reduce bus usage sooner
2. Easiest to hire and train CM for system branch by branch instead of all at once.
If they did this, PoP/AoA branch would be the last branch to open.