I grew up in a small city where my mom worked for a 35 doctor clinic which included the GPs and specialists.  Not only did the doctors have equipment that a smaller practice would have been unable to afford so that patients had quicker care, the doctors shared their expertise  in solving difficult cases.  
On a personal note, in 1990 my father was having a stomach issue and the doctor sent him downstairs to have an ultrasound.  The Tech decided to check out my father's entire chest area, noticed an aneurysm on my dad's aorta.  He asked dad to stay in the clinic and the tech called the internist.  2 hours later, my dad had his surgery scheduled in Calgary.