I manage two physician practices that are part of "physician partnerships" with a hospital which basically means that our practice is owned by our hospital. That does not automatically mean that the hospital is the entity solely responsible for the overhead. You would need to look at a few things such as how your Tax ID is registered, how your physician contracts read and what the relationship actually is. You may also need to check your local and state regulations.
In our case our POS for services performed in our office is 11, not 22. Even though our practice is hospital-owned, our physician organization has a different and separate Tax ID than the hospital itself does. POS 22 is only used for services in which the patient is actually being seen within a hospital department such as radiology, outpatient surgery, lab, etc. Do some research and contact the person responsible for credentialing your physicians and/or your group and you should be able to find a definite answer for your practice.