Tower Controller described an emergency return to the airport event; which became complicated because landlines were inadvertently programmed to the wrong position confusing coordination between the TRACON and Tower.

Narrative

Working Ground Control. East runway was closed; so we moved from our normal Tower and Ground East Positions; to the West Side Positions. Weather was exactly 1;000 FT and 3 miles as I recall. A PC12 departed on an IFR flight plan. There were 2 Air Carrier flights inbound on ILS. Within a minute of the PC12's departure; he apparently declared an emergency with departure and turned back toward the airport. I do not know if he was navigating visually; or via GPS. Someone in the TRACON called the Tower phone and said to send one Air Carrier around. We did not immediately know why. Then I noticed the PC12 descending back toward the approach end of the runway. About the same time; somebody in the TRACON called me and said the PC12 had a flight control problem and was inbound to Runway 17R and asked for landing clearance. I gave same; then told Local and advised Local to turn the Air Carrier flight to the east immediately as he began his go-around. I don't think Local knew what was going on; and I didn't immediately know why RADAR had called me on Ground rather than Local. We later realized the Local East Position had been improperly forwarded to Ground West rather than Local West. The Air Carrier flight did not react promptly to the go-around or right turn instruction. The PC12 wound up making another circle on right base. I do not know how close they got. I also asked the Supervisor to roll the fire trucks and got them on their way. RADAR again asked me for a landing clearance; which I gave and coordinated with Local West. The first Air Carrier flight behind the Air Carrier was sent around; and the PC12 landed without further incident. I have no idea whether the PC12 saw the Air Carrier flight or not. I have no idea how close they actually got; I was too busy coordinating; stopping ground traffic; and getting the fire/rescue equipment in place. Recommendation; this was an unusual aircraft emergency; and therefore impossible to predict or prepare for. The only recommendation I have would be to insure landlines are forwarded properly a couple times during shift.