On an ECN model broker, the prices an the screen "usually" reflect the best bid/ask prices of their respective liquidity partners. I say usually because there are some brokers using Currenex ECN platform that pad the spread by a pip and don't charge a commission, i.e. FXCM's platform. So for the most part, an ECN doesn't run stops because effectlvely they don't control the prices you trade with.
Now bucket shops, sorry, marketmakers/dealing desks, they create the price that is displayed. Through some type of algorithm and prices from their liquidity provider, this is the price that shows up on your screen. They can manipulate the price you see, and as such, can change the price to run stops, causing your trade to execute and they get their pip.
MBT is supposed to be an ECN, like Hotspot or IB, their prices are supposed to be controlled by their partners, not by some internal controls. As someone asked, what happened with MBT that makes you think your stop was run?