Okay, well, after giving this some consideration I would recommend contacting your primary carriers in the state the test is performed in. They may have specific guidance on any state law(s) that may pertain.
Considering that both services are done by the same company, same tax ID number (I presume same specialty of pathology?), it would seem that this would fall into a "contractual" issue where the "billing provider" receives the entire global payment and has a contract with another provider to perform a portion of the service for payment.
Having said that, it also would seem within the company there would be some type of policy on splitting payment for professional and technical components between the two providers. With that in mind, perhaps also check with your company financial officer.
I know this probably isn't a ton of help, but hopefully some.
Let me know what you find out, perhaps it will help me in the future.
Kris