Well,
from what I see the:
1. The PBX sends a call request
2. The Cisco accepts the request
3. The call gets connected and Cisco forwards the "CONNECT" message to the PBX.
4. And here is the important thing... the PBX
rejects the call with "No circuit/channel available".
And in the beginning (Q.931 SETUP)there is an error message:
**ERROR**: CCPMSG_InCall: Channel_ID IE invalid 96 (0x60)
Might be that the Bosch has a different numbering scheme (doubt that), or the channel is already occupied by another call (glare).
In this case, try to confrigure the B-channel occupying as ascending on side A and descending on side B.
Indeed, what protocol are you using?
ETSI/NET5 or QSIG?