One Russian girl told me once a very strange story. One or two years ago she married a French man. She was an atheist and she wasn't baptized one. But he was a catholic and he asked her for a wedding in a church after civil marriage. She said: "OK, no problem. If it is important for you I'll take baptism and we will marry in a church." But priests said that they wouldn't baptize her but they would gladly marry this couple. So they married without her baptism.
I don't know the situation in other EO Churches but in the Russian Church it is obligatory to fast at least for 3 days, to make a confession and to receive the Eucharist in addition to baptism before marriage. If one is not ready to do this then he isn't ready to marry in the Church. I can't understand how is it possible to administer such a sacrament as a matrimony without a baptism. I do understand that it is bad to baptize an atheist, but I think that it is much worse to marry without a baptism. What for?
Our standard practice is similar to yours, baptisms of Catholics, Protestants, and Oriental Orthodox accepted. But, with that said, I know of cases where marriages with Mohammedans, Jews, and even a Buddhist were approved without baptism or conversion; in the end, it's up to the Bishop, and fortunately we have Bishops out there that will say that, ultimately, it's up to the couple.
Oh, and all our marriages are sacramental...theology vs. practice may be messy at times, but it's pragmatic.