Not super knowledgeable in this but from a soviet history class we read a book by John Scott, Behind the Urals, whom went to the Soviet Union for work during the Great Depression. They were building a new industrial city called Magnitogorsk. So in short, industry had already started moving before the war itself to the interior of the country. Later on though I know that when fleeing from the western front the soviets basically sabotaged what they could like pulling up rail lines, burning farms, destroying factory equipment, etc. so the enemy would not get to use it against them. To what extent industry was moved in not sure; I just know that it was moving beforehand.