..isn't it still in pre-order status? You can't really buy it yet (at least I can't in Steam). First beta-test will happen at the end of the next week, and release is in September. So you probably just pre-ordered it, and will be able to participate in beta-testing, starting next week.
Check the latest news for BB2 in steam, there is date of the next betatest. Not sure who were those guys who played it, I believe they are known BB2 streamers of sort, so may be they were given exclusive copies. Or may be it was previous alpha/beta testing phase.
Next week there will be big stress test for all owners of BB2, and after that there will be closed beta phase for preorders like you.