All IPs which are connecting to Middle Realy, except the IPs in the consensus file are Bridge IPs?
Are there any other IPs possible?
The Tor network does not make any distinction about "middle" relays, so I'm assuming you mean a relay without the Guard or Exit flags.
In most cases incoming connections will be from guard or bridge relays, but not always. A Tor client is allowed to build circuits through any relays it wants in any order, so a Tor client may connect directly to a "middle" relay. Directory authorities may also connect directly to the relay in order to check if it's up. If the relay is acting as a directory cache, people may also download directory documents from the relay's DirPort. I'm not sure if there are others.