Commentary for Avodah Zarah 61:11

R. Judah b. Batera classifies three different types of wine. The first is wine that has actually been libated. Such wine is considered to be a by-product of idol worship. It is forbidden to derive any benefit from this wine. And it causes impurity. Wine that belongs to non-Jews is not considered to have been involved in idolatry. But it is still forbidden to derive benefit from it, and of course to drink it. Its defiling properties are lesser—it only defiles food and drink.
If the wine belongs to a Jew, but the non-Jew was holding on to the wine, then the Jew may derive benefit from the wine, but he may not drink the wine.
Note that there seem to be two issues combined here. The first is contact with items used in idolatrous ritual. This would apply either to wine that had actually been libated, or to wine that might have been libated. The second issue is preventing contact with non-Jews. Wine simply owned by a non-Jew does not need to be treated as an idolatrous product. But if the goal of this halakhah is to prevent fraternization, then prohibiting any contact would make some sense.

En-Kushi, Borkata and Zagdar are Samaritan cities while Birat-Sirika, Kefar-Parshai and Kefar Shalem are non-Jewish cities. Originally they prohibited the wine in the Samaritan cities due to their proximity to non-Jewish cities. But then they relaxed this law and allowed Jews to drink Samaritan wine if the cask had been closed up.