Would redirecting them to a website where they can go through a guided intake and get some confirmation of a callback? A well designed UI that allows them to ID their vehicle (make/model/year) and the issue they're having? HTML5 has decent speech to text out of the gate and they can just talk it out.

Obviously that process could happen purely via voice but I think there's not as much love for walking through forms in a phone call.

If Joe has a PC in the shop with a tailored UI, he could get pings of pending requests and when he comes up for air, update the intake (via voice to minimize greasy hands) and initiate a call back then and there?