How did the World Government know about the clash between Revolutionary Army and Blackbeard Pirates? As the recent manga release of One Piece, we all know that Jesus Burgess infiltrated the Revolutionary Army HQ (Baltigo) and reported it to his Captain BB. 

My question is how did the World Government know that the Blackbeard Pirates were planning on attacking the Revolutionary Army HQ. we could take note that the one who attack in Baltigo are Cipher Pol, not the Marines. 

As I remember, Cipher Pol is directly serving World Government (Nobles). Even if that Information came from marines first. How did they know? Is Aokiji a spy?
I can think of one possible solution. The black den den mushi which can spy on people's conversations. I'm guessing that the world government (CP0 or the Marines) were either near Blackbeard or near Baltigo originally spying on either Blackbeard or Baltigo (since it is a suspicious country). Once they tapped into the conversation, they got confirmation of Dragon's location. 

The other assumption is that CP0 followed Sabo from Dressrosa to Baltigo. After following them and finding their hideout they planned a full out attack but got there to meet the place in ruins due to the Blackbeard pirates. I doubt that they followed Sabo since the Revolutionary army were secretive and careful about everything they did.