Working Two Different Specialties-seeing the same patient

[ProfPA]

Hi! Asking for a former student...he's working for two different specialists at the same hospital. Some days he's working for the psychiatrist, other days for the GI doc. The GI doc always comes in and sees the patient as well, so that is billed as a shared visit. The psychiatrist is never there, so the billing is under the PA number. There are some occasions when the PA is seeing a GI patient, and the attending or nurses have psychiatric questions as well. Since the GI doc is billing under his own number and seeing the patient as well, can the PA bill for psychiatry services? So the PA is seeing and writing a note for two different services? Or is this fraudulent? Thanks!