Leaving my hotel one morning this week, around 6:30am and before commuter traffic had really started, I noticed there were eight of their scooters line up just outside the exit of the hotel. I maid a point to walk by other hotels on the way to work and about half seemed to have them outside. By 8 or so, they were gone.
So, to answer your question: I assume there are a bunch of couriers or "Field Agent" style gig employees that walk around the downtown and collect them, and that they have an app that shows the last known location of each one. I also assume that there is a van somewhere that picks them up once they're collected, takes them somewhere to charge at night, and then drops them off at hotels and transit stops before the morning rush begins.
[...] charge Birds at your home or office. Earn up to $100/night. $5 per battery, up to 20 birds