Chad Yakobson say: In 100% brett fermentations, his brett strains don't like to ferment/finish below 68F or so. I'm sure it depends on the strain, but he gave this as a blanket statement, assuming across all strains he uses.
In a mixed fermentation with Sacch and brett, brett will continue to work during conditioning, even at low temps, albeit much more slowly. I can't speak to the differences in flavor profile, but I assume there are some.
Lacto and pedio pretty much go dormant, permanently as far as I can tell, after cold conditioning. I've tried mixed fermentation with slurry from kegs that were previously in the kegorator - not much funk, hardly any acidity.