I have not seen anything in particular other than the contract does allow the season not be ever be aired, in which case, the teams would not receive any prizes they were to have won. The bona fide external emergency situation is one that is unclear. From what few aimilar instances I have seen, the production soes not take a pause unless necessary; as in last minute substitution of a leg due to civil, military, or natural disasters (which have occurred several times, including season 27 for leg 11). The first leg you are referring to, the race proceeded, and as far as I know, no time credits were awarded, that type of situation being one of the everyday risks of air travel.