depends on the exchange (i'm calling ECN's exchanges). If a data vendor can get a feed so can a brokerage (at a price). Perhaps I should reconfirm what we are doing in the states but given IB Groups volume (usually well over 100 million NYSE shares per week), I'd be surprised if the feed did not come from the exchange source. In the markets that I trade, we get the feed from the exchange when possible and not prohibitively expensive.