Never said that all of them were used by the mine and torpedo regiments, btw. Just a significant amount of them. Nothing sudden about it either. In my short life, I've know that fact for about 15 years now. Maybe you shouldn't casually talk about how lend lease aircraft can cover the Soviet bomber aircraft need when you don't know much about their use in the Soviet Union in the first place?
"As early as September 29, 1939, Douglas received a Soviet offer to purchase ten DB-7s and a license to produce them in Russia, along with a license to build Wright R-2600 engines. Those negotiations were ended by war in Finland and the resulting weapons embargo. In September 1941 the situation changed as the Nazi invasion added the Soviet Union to lend-lease programs.
Since the Havoc was produced to give close support to ground troops, and since the largest Allied army was Soviet, the USSR was allocated 3,125 Douglas Havocs at a promised rate of 100 a month. Of these, 2,908 actually arrived, including 869 flown over the South Atlantic and 550 shipped over to the Persian Gulf, plus 126 shipped to North Russia.
Another 1,363 were flown over the Alaska-Siberian (Alsib) route, the first 12 A-20Bs leaving Ladd Field with Soviet pilots on October 6, 1942. Regular deliveries were completed in July 1944, but the last 97 A-20H/Ks were added in May/August 1945, to replenish units to be used against Japan.
The first DB-7Bs for the Soviet Union shipped via the South Atlantic and Persian Gulf, began arriving at Basra in February 1942. Since the first to arrive were 77 Boston III (DB-7B) and 103 IIIA (A-20C) aircraft originally scheduled for Britain; they were designated B-3 in Soviet service, and entered combat on the Southwestern front in May 1942 with the 794th Bomber Air Regiment (BAP). DOUGLAS A-20K-15
When joined by the 57th and 745th BAPs, they formed the 221st Bomber Air Division. Beginning in September 1942, a Soviet UTK-1 turret with a 12.7-mm UBT gun replaced the .30-caliber guns in the open rear cockpit. A-20s replaced the standard Pe-2 light bombers in 12 Red Army (VVS-RK) air regiments, including the 45th, 449th, 860th and 861st BAPs of the 244th Bomber Air Division; the 63rd, 277th, 367th, and 542nd BAPs of the 132nd Bomber Air Division, and the separate 201st BAP.
Cameras were introduced in July 1942 for reconnaissance by A-20Bs of the Baltic Fleet’s 15th RAP and by the Black Sea’s Fleet’s 30th RAP in November. Two torpedoes test launched from a DB-7C in March 1943 showed that a Boston could handle those weapons better than the II-4s then used by Soviet crews, so 36 A-20Bs were modified for torpedo attacks.
While American crews did not use the torpedo provisions added under the A-20G’s fuselage, torpedoes became standard for the five Soviet Navy (VVS-VMF) Mine-Torpedo Air Regiments (MTAP). The 9th Guards MTAP and the 36th MTAP, operating against German convoys near Norway, the 1st Guards and 51st MTAP in the Baltic Sea, and the 5th Guards MTAP in the Black Sea, used A-20Gs modified for four crewmen with windows added in the nose and behind the turret.
A Soviet airborne intercept radar, Gneys-2, was tested on a few Pe-3 night fighters and a Boston III, and production ordered on June 16, 1943. The lend-lease A-20G-1 was considered the best type then available for night fighting because of its forward firepower and the space available for a navigator and an operator of the Gneys-2 sets added to the planes at the Monino modification center. Extra 274-gallon bomb-bay fuel cells were added, but the flexible guns were usually removed.
The 45th and 173rd long-range night-fighter escort regiments (APON), of the 56th Fighter Air Division, each had 32 A-20G-1s. Like the AAF P-70s, they were seldom able to line up their guns on enemy bombers, flying 650 sorties in 1944 without definite result. The German night attack upon the U.S. bombers landed at Poltava showed the limitations of VVS night defense measures.
When the war with Germany neared its end on May 1, 1945, 127 A-20B, 105 Boston III/A, 147 A-20G-1, 115 A-20G-10, 376 A-20G-20, and 65 A-20J/K remained with the Red Army (I count 935 - arlo). Navy units also had 43 A-20Gs with the North Sea Fleet, another 43 with the Baltic Fleet, and 70 with the Black Sea Fleet (I count 156 - arlo). War against Japan in August 1945 involved A-20s of the Red Navy’s 36th MTAP, 49th MTAP, and 50th MRAP regiments. The 36th MTAP was still flying A-20s from Port Arthur on September 4, 1950, when one was shot down by F4U-4Bs from the Valley Forge.
http://www.americancombatplanes.com/a20_5.html
It seems there's more availability for their historically accurate use in a scenario than there is an Italian skinned bomber of any kind.

(to be cont.)