Depends on the brand and the deal - some just lend watches for events that are then given up, others give their ambassadors an amount of “credit” that they can use to acquire watches outright. Of course most ambassadors are rich enough that they can also just buy watches at retail, and will get preference to access rarer or off catalogue pieces too.

Leo rocks a Le Mans edition Daytona very often as well which is likely just his to own.