The Phone Port Primary Line determines where the call is routed. Read my explanation of the Phone OutboundCallRoute in your other thread.
Physical Interfaces -> Phone Port -> Primary Line: SP2 Service
Alternately you can route calls selectively with additional code.
Leave the Primary Route set to SP1 Service
Add the following to the beginning of the Phone Port OutboundCallRoute
{911:sp2},
Now 911 will be routed to SP2 and everything else routed to SP1.
You can route any number this way as long it is unique (i.e. area code 480 to SP2)