you cant scout yourself to see what armies he sent to put down the rebellion. Nor can you see them comming with your signal beacon. There is no way to figure out what the suzereign is bringing into battle..but he can scout you and know exactly what you have!

Now of course you can scout the enemies city..and hope to catch a glimpse of what he COULD send, if he wanted. BUT to find out what he actually DID send? So far I havent heard of any way to do it.