I think the answer lies somewhere in the middle.

I actually wrote a paper about the grain trade between the Soviet Union and the United States and how that trade affected Rural American's during the 70's. After Khrushchev began the focus of maize based products to feed a rising livestock population in the Soviet Union and the failure of setting up the maize industry within the Soviet Union, they eventually began to buy corn and feed from countries outside of the Soviet bloc; ironically they bought a large amount from the United States. The corn was bought by the use of gold and foreign currency, because the Soviet Ruble was not accepted outside the Soviet Union. The United States enacted a grain embargo on the Soviet Union because of the invasion of Afghanistan at the end of the 70s, the key event for trade here is that the US Government made necessary provisions for US farmers to receive subsidies to account for the lose of trade with the Soviet Union. The Soviet Union did not suffer, because they instead turned to Canada who gladly supplied them the corn they sought to buy, and some American farmers sold their grain to Canada that ended up in the Soviet Union regardless of the embargo. The paper, I believe, concluded that the embargo did not have a dramatic effect on grain prices in the Soviet Union, but it was feared that it would.

The Soviet Union used trade to increase its own foreign currency to feed back to acquire goods that the Soviet Union could produce itself. A major export for the Soviet Union was oil. They also worked hard to find and produce gold and other precious minerals to use as a trading tool with the outside economy. The mine and massive Gulag in Kolyma was incredibly valuable to the Soviet Union because of its effect on world trade.

Therefore there was definitely trade with the outside economies, however it was always State-to-state or State-to-Company, and was not company to company, or the most characteristic of capitalism, company to person. The citizens of the Soviet Union were largely exempt with foreign trade and it wasn't until the last years of the Soviet Union that it became more involved in world trade.

The point is that the Soviet Union was the participant in the global economy as itself. Not as a body of people that could be sold to. The Soviet Union used the global economy for their own means to acquire goods that they could not produce them self. This meant that they would trade things they had in exchange for things they did not, at the governmental level. For example in the early years (before the Cold War) Stalin's government sought to purchase manufacturing machines and used hard currency, gold, or grain to do so. This ties in with the Grain Famine of 1932, because they still exported grain even though it was during a famine because to not do so would hamper the route to industrialization. Later they would use arms trading in conjunction with oil, gold, and agricultural goods to purchase outside goods for use within the Soviet Union. Therefore the Soviet Union was an outside participant in the global economy, not part of it.