Sure, that's why they quoted from it.. because they weren't bound by what they openly proclaimed as "God's word". They never stated they were not bound by it. They stated they were not under the law. And that is quite another matter. Now you're grasping at straws.
And, no, I don't believe it was by accident that Greek was the language chosen anymore than the fact that Hebrew was the original language used for the Old covenant. If you ever get a chance to listen to Chuck Missler speak on the Hebrew language, I'd highly recommend it, btw. The information he emparts about it is astounding. The Greek is the best counterpart to Hebrew for what it is capable of conveying - level of specificity, etc. It's the perfect language for the task. So, it is no accident that the NT texts originated and came down to us in Greek.