According to Pg. 67 of the BRB, when emergency disembarking, "the models are deployed anywhere within 2" of the vehicle's hull, but the unit can't do anything else for the rest of the turn." On page 9 it defines turn as "Whenever the rules use the word 'turn', both in this rule book and in the Codexes, [sic] it means 'player turn', otherwise it will clearly state 'game turn'."
So, if a vehicle is destroyed by my opponent, and the exits are blocked, that means that I can emergency disembark without ANY actual penalty? (As the restriction that the unit can't do anything expires at the end of the player turn...)