Adopting a medically fragile child - ins. question

My sister's two adopted children are on her private healthplan and have medi-cal as secondary. The way it works with them is medi-cal pays whatever the primary insurance won't pay. Medi-cal doesn't care why the primary insurance didn't pay, just that it didn't, so she can take them to doctors that she knows are outside her primary insurance's plan and Medi-Cal will still pay. She has done this a few times when she wanted them to see a specialist outside their regular plan.