The other site is managerzone.com... There you are the manager and coach of your team, buy and sell so as to have good players, build your tactics, train your players in the training fields so they get better. And the main difference in comparison with PS is that you don't control your players; they play automatically -you can watch the matches, though-. I think Power Soccer is better because of many things... Nevertheless, nowadays I play both games :) I think the used to have a game on facebook, "footy!" I think it was called. But I think MZ is the only one, acording to Power Challenge's official website.
Only Managerzone. But I know a Russian Power Soccer xD but now is closed.
It's Power Soccer for the people who live in the countries of the old USSR, not only Russia, and I hear that it's not just doing well, but actually thriving, so it isn't closed.
Now, by "closed" you mean that it directs you to powerchallenge.com... instead of ligaonline.ru , and that happens since it was fixed so people of other countries from USSR to not be able to make an account there.
On topic, I believe this isn't a game owned by PowerChallenge Company, because the Soviets had bought all the rights for it.