I'm in Texas and below is what BCBSTX told me about billing for NP's and PA's. I've also seen this posted to other Blues plans as well. Because the Blue plans has Blue Card set up to bill claims as primary to your local BCBS plan for most Blues plans you will need to follow the directions of the Blues plan is in your state. You can also bill a PA and NP services as "incident to". Access the website for your local BCBS plan.
Since they are out of network, to bill you would use the MD/ DO's rendering NPI # as the performing with the appropriate modifier "SA" or "AS" on the claim.
Thanks,
La Shunda