yiucsw,
The simple answer is to dial OBiON > SP2
To do this you need to change your OBiTALK InboundCallRoute. I'm using an OBi110 in this example, Its Primary Line is sp1. Delete existing and replace with:
Voice Services -> OBiTALK Service -> InboundCallRoute:
{(Mcot)>(Msp1):sp1},{(Mcot)>(<**1:>(Msp1)):sp1},{(Mcot)>(<**2:>(Msp2)):sp2},{(Mcot)>(<**8:>(Mli)):li},{(Mcot)>(<**9:>(Mpp)):pp},{(Mcot)>**0:aa},{(Mcot):aa},{ph}
User Settings -> User Defined DigitMap 2:
Label: cot
DigitMap: (290123456)
Where 290123456 is your OBiON softphone number.
Now you should be able to dial from OBiON in the same way as from the phone connected to the OBi110. To dial out using sp2 from OBiON simply dial **2 followed by the number.