HTIMS: This suggests a misunderstanding of how E911 calling works.
Google Voice doesn't support E911 calls at all. You don't select which of your two Google Voice SPs to use; there is no "cheapest route" for 911 calls. Instead, you subscribe to E911 service from another service provider, such as Callcentric or Anveo. You set this up on a third SP. 911 calls do not go through either of the Google Voice SPs
The OBiTALK configuration page will simply ask which SP to use for 911 calls, and then it will automatically build the correct digit map, to recognize the 911 digits, and send those calls out via SP3, regardless of whether your default
SP for regular outbound calls is SP1 or SP2.