Thermal switches normally control the temperature range. However, on freighters and, optionally, pax/combi aircraft, the cargo areas can be treated as an extension of the cabin air-conditioning system with variable temperature control.
Optional temperature ranges for the carriage of live animals (e.g. pets) are switchable on the more basic systems.
Are you questioning the ability of these systems to maintain the temperature range, or are you coming from a different angle?
Regards
NSEU