Flixbus owns 1 bus I believe, just so they can apply for routes as a bus company. They then "wet lease" the services (staff+bus).
It's a bit more complicated. We have a revenue share model with our partners, payout depends on a few factors and is about a 70/30 split. Though we also guarantee most of them a minimum payout per ride. So it's in both parties interests to have satisfied customers.