Hi,
You can find out how many IP channels are occupied by finding out what PBX numbers have the 2 PBX's.
You need to do an STATE XNET ALL so find the PBX numbers, after that you need to type 
STATE XNET ICP <icp pbx number>
It's something like that
Signalling   |  Link  | Dest |   XNET   | State        |  Owner  | ID  |Status 
Dvc Location  | Handle |Switch| Trunk Id |              |         |     |       
------------------------------------------------------------------------------- 
 1 1 11   1   |     12 |  141 |   269    |Busy          |Call Proc|7 191|Wait   
 1 1 11   1   |     12 |  141 |   177    |Busy          |Call Proc|6 1B7|Wait   
 1 1 11   1   |     12 |  141 |   590    |Busy          |Call Proc|4 21D|Wait   
 1 1 11   1   |     12 |  141 |   349    |Busy          |Call Proc|2 23C|Wait   
------------------------------------------------------------------------------- 
The destination switch is the PBX number (141) . The trunk ID as you can see is a random number
because they are virtual channels. Unfortunately you can't see what extensions are involved in call.