I feel that it is strange why Wang did it. Or at least why at that particular time after so many years. It might never happen.
1) someone just made it up originally. It was a logical prediction based on the fact that Wang was suddenly sacked.
Assume that it actually happened, the news could get out in the following ways:
2) A worker who is processing letters, making copies, etc. in 中央紀律檢查委員會 just leaked it accidentally or intentionally.
3) An enemy of Bo in the committee leaked it intentionally. This can only happen when the enemy believes that the accusation from Wang would be ignored. Otherwise, it seems to me that keeping the investigation secret is a better scenario for the Bo's enemy.
4) A visitor of 中央紀律檢查委員會 might accidentally saw it and leaked it.
Of course, the aforementioned scenarios are simply speculations without any supporting facts.
