PCV to C.I. joints

I work in a 15 year old building which uses all PVC above grade and C.I. below grade. I had always assumed that the joints in C.I. bell were done with a rubber donut, but I recently looked closer and found that they were done with lead.

Are these joints done using oakum and lead as was done with a regular CI joint? I have heard of alternatives such as lead putty or epoxy and am curious as to what is common in today's commercial plumbing?

Where I am, if there is cast below grade there is cast throughout the entire building.

Most new commercial uses cast drains here... And they certainly don't use any lead...

Most cast iron is assembled with No-Hub, MG couplings, or Ty-Seal "donuts". Environmental concerns have pretty much consigned lead/oakum joints to the museums, other than for attaching flanges to closet bend, or repair work.

What I don't understand is that lead melts at about 600 degrees, which is higher that the melting point of PVC.

These joints are 4" pvc into 4" bell C.I. and look perfect with no sign of heat damage anywhere around the pipe. Because PVC has a larger OD than cast, the lead line is only half the thickness of a standard CI to CI joint.

Are you sure it's real lead? Hard to imagine, due to that difference in melting points. My can of plastic lead looks real enough after curing.