I found a way to do this. By saving the current building object, we can change the active GMSIndoorDisplay level, and then force the delegate to be called:
- (void) didChangeActiveBuilding: (GMSIndoorBuilding *) building [optional]
Thus, the following delegates will start automatically: - (void) didChangeActiveBuilding: (GMSIndoorBuilding *) building [optional]
- (void) didChangeActiveLevel: (GMSIndoorLevel *) level [optional]