Vanguard Brokerage Services disclosure about order flow payment can be found at:

http://vrs.vista-one-solutions.com/reports/1-6/vang/

Short answer is that Vanguard Brokerage Services did not receive compensation for equities order flow in 1QTR 2015, but did receive compensation for options order flow.

I have no idea what the laws are surrounding their index funds or how those index funds are allowed to/actually do interact with Vanguard Brokerage Services.