They handle real-time events exactly as your latter example stated: an external (licensed) company provides live data, and orders that were placed during a dangerous situation (e.g. one-on-one) are subsequently voided if a goal is scored.
Why did you edit away your claim that it is to the benefit of the customers? Being a market-maker and being able to void any trades that occur during volatile periods sounds like a dream to me. No need to worry about adverse selection eh? Just printing cash with fat bid-ask spreads and if anyone dares to get the jump on you, they get voided. I wish I could do that in the real markets.
I can't speak for all companies, but some companies I worked with with honour those bets (places just a second before the goal). They try to find a pattern and ban the users after they find them doing this (and it is getting harder since live feeds are faster and faster) but I never saw a company voiding a bet because of this.
