I've commented before on the advantages of the Kaiser Permanente system, as opposed to the system of independent doctors, specialists, and testing labs found elsewhere.
Currently I'm gaining some (vicarious) experience with dentistry. While Kaiser includes some dental coverage, it's not in-house but run through a separate organization. It includes a directory of participating dentists, endodontists, and oral surgeons which are in-network. For a variety of reasons (not rational ones, but human ones), we're getting the work done outside the plan.
One difference between the medical side of our health system and the dental side is technology. The various dentist/specialists have a lot more technology in their office. Where doctors had to send you out for blood tests, dentists have x-rays in their office, while the endodontists and surgeons have even more equipment.
One similarity betwen the system is the referrals from dentist to endodontist and surgeons. It seems to an outsider there's likely an informal network in existence; whether the network is more than just mutual trust I don't know.
From the patient's standpoint there's still the frustration of repetitive forms: health histories and legal documents. Within the Kaiser organization, that's avoided for medical issues.
For any complex issue, there's a coordination issue. That's likely true within Kaiser for medical issues, especially when you involve a hospital.