Nephrologists do control hemodialysis and so if the group wants to keep it internal it would be challenging to compete with them. One would need to establish a longitudinal continuity practice for HD patients. There is definitely a role for IR in this arena, particularly in the outpatient office based lab as IR can do such breadth of procedures. UAE, vertebroplasty, peripheral arterial disease, varicose veins, fistula interventions, oncology etc.
Though it would be feasible for an IR group to manage a DR group and has happened in smaller markets. If you have a true clinical practice, you will have admissions, rounding responsibilities , clinic, consults and growing patient base. This will make it harder and harder to perform high volume , high quality imaging interpretations. Though you can finish PGy4 with a fairly solid foundation in imaging, you will become farther and farther removed from diagnostics as your last 2 years are clinical and procedural based. This will make you a better global physician, but will be challenging to be as strong a comprehensive diagnostician (neurorads, peds, MSK, Head and Neck, Nucs, mammography, US, fluoroscopy, cardiac, Thoracic etc). It is feasible that you can be decent at vascular imaging and body imaging but again with clinical responsibilities your time to spend on formal imaging will be less.
There will certainly be challenges in the upcoming years as IR training continues to transition and as the younger guard starts to demand clinical non procedural time to provide quality care to their patient base.