I understood you correctly about inbound calls. I don't know how you are routing calls to/from Asterisk, so I gave you my complete setup. I route inbound calls to the IP address and port of Asterisk. When you enable X_SpoofCallerID, the CallerID will be sent to Asterisk instead of the AuthUserName.
How are you currently routing calls to Asterisk?
Assuming GV is defined on SP1 and an Asterisk extension is defined on SP2:
Voice Services -> SP1 Service -> InboundCallRoute:
sp2(900@192.168.1.100:5060) (Asterisk IP address and port, 900 = extension#)
Service Providers -> ITSP Profile B SIP -> X_SpoofCallerID: Checked
The above did not work on my OBi200. I was able to circumvent the problem. Since you have an OBi110,
I won't go into details.
The above worked on my OBi110, but the firmware is down leveled at build 2824.