I'm not familiar with Mitel/Aastra. This is a setup for Asterisk.
Asterisk:
Setup an outbound trunk without registration for the OBi110:
Peer Details:
type=peer
username=OBi110
host=192.168.1.110 (IP Addr of OBi110)
port=5060 (Port# of SP1)
fromuser=OBi110
canreinvite=no
insecure=invite,port
qualify=yes
Setup an outbound route for above trunk
Setup an inbound route for 900 (See OBi110 Line inbound route)
OBi110:
SP1 must be defined as an SIP trunk to send/receive to/from Asterisk.
Setup a dummy SIP definition like this:
Service Providers -> ITSP Profile A -> SIP -> ProxyServer: 127.0.0.1
Service Providers -> ITSP Profile A -> SIP -> X_SpoofCallerID: Checked
Voice Services -> SP1 Service -> AuthUserName: OBi110
Voice Services -> SP1 Service -> X_RegisterEnable: (unchecked)
Route outbound calls from Asterisk to Line
Voice Services -> SP1 Service -> X_InboundCallRoute: li
Route inbound Line calls to Asterisk
Physical Interfaces ->Line Port -> InboundCallRoute:
sp1(900@192.168.1.100:5060) (Asterisk IP address and port)