Technically, individual IP trunks do not use C-LAN resources or sockets, the signaling group associated to the trunk group does. So an entire trunk group of IP trunks only uses approximately the same amount of C-LAN resources as a single IP telephone. So you could have hundreds of IP trunks controlled by a single C-LAN with no problems. A C-LAN has around approximately 400 useable sockets, but it is recommended that you don't use more than 200 - 250 of these (a single signaling group uses 1 socket, an IP telephone uses 1 socket, etc).
I hope this helps.
IPSI