If the bottles are radio active, then wouldn't it just be a matter of time before the contents have the same problem, even if they were spared the original blast of radiation?
And true, wild yeasts may not be the correct style for what we're brewing, that's why it'd be more likely that you'd end up brewing to match the yeast more than adding yeast to match your brew. It's also why cider and wine was such a strong suggestion, they'd grow with enough natural yeast to start furmentation. Though, if you could track down a bottle in the style you're looking for on lees, then you'd have hit a gold mine! But that'd be tough.
Also, I know it's not supposed to be mentioned, but if there is a collapse, then distilling is back on the table. Whatever nasty, nearly drinkable beer/wine you brew could easily become something marketable.