Those are early Boston IIIs, not A-20G Havocs. See the nose and the cheek 30cals and the rear gun position?
Reading an article not too long ago, the US removed the cannons because of reliability issues and constant jamming.
Whether the Soviets put their own cannons in, this would be a field mod. I'm also curious (not having seen so far) how many cannon armed models they used, compared to MG-ships.
P.S. Soviets modded everything. They put 2x 20mm SHVAK and 2x 12.7mm into hurricane Mk.1s and Mk.IIs, rather than use default setups.