Just wondered if it was possible with PRE 10 to "grab" a clip from an ingested stream by marking In/Out - while the stream is being captured.
Standard video editing software, such as Premiere Elements or Premiere Pro, doesn't provide that capability. You can certainly capture live from a camera, but you must manually start and stop the capture to create a file which can be subsequently used in the editing software.
Broadcast applications, such as the ones you mentioned, ingest to a video server which has capabilities to define and grab a segment on the fly. The server can handle the routine functions of green screen, slow or stop motion, reverse play, and overlay without the need for external editing. Of course, once created, segments can be edited by an external editor such as Premiere as well.