调查组初步调查 and 立案调查 are two different things.
There could be 初步调查 before Bo was sacked. As a matter of fact, it is almost certain that there was some kind of investigation since it was quite long between the time when Wang came to Beijing and the time when Bo was sacked.
Bo's supporters performed a great show during that time. We should do 立此存照 about that.