I'm no plumber, but I replaced my neighbor's sanitary sewer, and all I needed (aside form the proper permits) was to have the township sewer guy inspect it. In the next county over, I'm not even allowed (technically), to help the licensed plumber handle the pipe. The county plumbing inspector has to look at it before it can be backfilled, and depending on the municipality, so might the municipal inspector.
Digger and I are from the same neck of the woods, and I've had the same experiences as him. The county we live in doesn't require much in the way of licensing for building trades.
I've done sanitary sewers and only had to have the inspector from the sewer authority see that the pipe met their spec, witness the pressure test, then witness the backfiling with the required amount of gravel.
Also installed ductile iron water main for a sprinkler feed, and it was basically the same procedure, although in that case, the sprinkler company handled the pressure test.
In most cases the municipal authority will deal with installation of taps to the mainline, and leave you with a stub or shut-off valve to connect to.
Hey Digger, I assume the "can't touch the pipe" statement is the case in Allegheny County?
I'm working on a bid right now for a sewer connection, but at 8ft deep, and only 25ft long, it's not one I really want to mess with. When the holes start to get that deep, they give me the willys...
Joe