I am not sure if this is still the case, but up to 20 years ago, these were typically shut off in May-June to August for “maintenance” which resulted in a prolonged period of no hot water in apartments.
>>xattt+(OP)
In Moscow? Never. It's been usually a month in soviet times, two weeks max nowadays, usually sometime in late June - early August.
edit: also on heating question - Moscow's electricity is provided by 40 or so big gas-fired steam turbine generator plants, about 10GWe total. District heating serves as cooling for all this power generation.