This is variable depending on specific insurance contracts. This has nothing to do with Stark law, since you are just referring your own patients to your own employees in the same practice. If this violates Stark law most of the medical practices/hospitals in the country would shut down.
More commonly however, the situation is reversed. E&Ms are commonly out of network, due to high demand. Therapy is often in network within a large mental health practice, as therapists are numerous, and panels are often not recruiting therapists. Owners of the practice typically would extract some excess value from the insurance reimbursement from therapists, not as much from E&M since labor cost higher. In-network MDs can often become a cost center to recruit patients for much more favorably reimbursed (vs. labor cost) ancillary services. This is a typical model for Medicaid driven practices (i.e. invariably they lose money for MDs, but they will need them to 1) keep grants, 2) get reimbursed for "group therapy" that actually floats the program).
Look, you are thinking too much right now about all of this. The ins and outs of how to execute this correctly will depend on the specifics of the particular practice you join/start. If there are ambiguities on the regulatory side, you can find a lawyer who specialize in this and can consult. There's no straight answer to provide on SDN because each practice/contract is unique and depends on the geography.
