Regarding the trigger(s) to long lived bees, Döke, Frazier and Grozinger wrote:

Integrating the available information, we suggest that the
entry and exit to the overwintering state is mediated by
interactions between environmental nutritional
resources, brood/brood pheromone levels, forager pheromone,
and potentially temperature and photoperiod cues.

Interestingly, supplementing
or restricting colonies’ access to pollen in fall
do not impact the number of winter bees produced, their
physiological nutritional stores, or their performance, 
and thus factors _other than fall nutrition_ 
(perhaps genotype and/or parasite/pathogen loads and/or 
resource availability throughout the season) seem to
regulate the population size and performance of winter bees

Further, they stated:

Colonies headed by local queens survived an average of 
83 days longer than colonies headed by non-local queens.

However, it is unclear if the effects are due to local
adaption of the survivor stock, or simply that queens
produced by local beekeeping operations are of higher
quality than those produced by large-scale commercial
rearing operations.

Recent studies from our group have not found any evidence 
for local adaptation of honey bees stocks to winter conditions
(Doke, Frazier and Grozinger, in prep).

Döke, M. A., Frazier, M., & Grozinger, C. M. (2015). Overwintering honey bees: biology and management. Current Opinion in Insect Science, 10, 185-193.

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