I'm OK with being half right
Here's the answer to the other half of the question:
To forward all incoming calls on sp1 to a number via sp2 these values can be set:
Voice Services > SP1 Service > Calling Features > CallForwardUnconditionalEnable: Checked
Voice Services > SP1 Service > Calling Features > CallForwardUnconditionalNumber: sp2(011441179123456)
This can also be done using Star Codes, but is messy and requires script changes to specify one specific trunk.
The easiest way to forward all incoming calls on sp1 to a number via sp2 is this:
Voice Services > SP1 Service > X_InboundCallRoute:
{sp2(011441179123456)}
Normally Voice Gateways are set up to allow more options for outgoing calls and they are added into the Phone Port DigitMap and OutboundCallRoute so they can be dialled from the phone attached to the OBi. See here:
http://www.obitalk.com/forum/index.php?topic=526.msg3124#msg3124However, if you only wish to use it to forward calls as described above, then you only need to refer to it in the sp1 InboundCallRoute:
Voice Services > SP1 Service > X_InboundCallRoute:
{vg3(011441179123456)}
Voice Gateways can only be used for outgoing calls using a voip provider that does not require registration.