We have no separate certifications for nurses here, and who we talk to depends on where we transport to.
At the trauma center, two nurses staff the ER Communications Center- answering the EMS phone, taking calls for transfers from MDs, and monitoring the statewide hospital diversion website. When we call in, they answer, and we tell them if we're making notification or need Medical Control. For the latter, they usually either transfer us to their partner's phone or out to Ambulance Triage for pre-arrival report ("Are they critical? No? See you when you get here."). If we need Med Control, one of the Comm nurses grabs one.
At most of the smaller community hospitals, the charge nurse answers, and transfers to the doctor's desk if we need that.