This is indeed an interesting thread, and the question is equally intriguing as to whether or not MMA training will ensure survivability in a street fight, well here's my two cents:
I will not reinvent the wheel here with this one, there are factors which change the possible outcomes, and they run the gambit from physical to emotional with everything in between, that being said I think there's three Laws of Combat that could apply to dynamics.
1. You are NOT a Superman!
2. If it is stupid but works, it isn't stupid.
3. Anything you do can get you shot including doing nothing.
What each contendor wishes to accomplish in the engagement can be two entirely different things, and that can lead to a raising of the stakes to lethal levels very quickly in a street fight. In MMA matches the goal is the same: victory; the goal behind the drive in each contender to win however will be different, some for fame, some for money, some for revenge, and the list will go on. In each case a persons approach to a situation changes as their perceptions and this can be an advantage or disadvantage if caught. If you know that person 'X' feels bad about his buddies laughing at him for not scoring with the 'princess' across the floor and he wants to still prove he's got bigger bits and pieces than them by taking on someone he thinks is an easy target, you know he won't be expecting a quick blow to the eyes, and legs with a choke hold following. A trained and seasoned fighter will instinctively take note of their opponents size, especially if they have advantages and disadvantages relevant to the outcome of the fight.
To sum up: Matches for sport are usually in controlled environments with as many external factors eliminated as possible making it more technical, unlike street fights which force you to be a bit more aware. Learning to see underneath the underneath keeps the most logical outcome, the easiest to attain. However, imo, the best people to ask about this sort of realistic type of situation are members of the military, especially those who have experience in close quarters engagements.
Success cannot be attained except by piling effort upon effort.