I've never seen HR use data brokers. I would think that could open them to a lot of risk, finding out things that aren't legal to know about someone before saying yes. All of mine have used actual background check agencies

Can you clarify if you're looking at a field where background checks are mandatory (like security) or one where the employer is voluntarily running one? In the latter case, brokers are usually cheaper and more common, in the former it may be mandated to go through a specific government entity i.e. county/state/province law enforcement - often times that will be dictated by contracts with clients, sometimes laws.

I don't think there has been any confirmation for this practices beyond speculation... yet