It is possible to access the internal statistics of rtpbin using its get-internal-session property.
g_signal_emit_by_name(rtpbin, "get-internal-session", 0, &session);
Then I can use the RTPSession object to access and set properties like rtcp-min-interval or callback another function when a signal like on-receiving-rtcp is emitted.
How can I do the same using webrtcbin? Are the properties/signals of the RTPSession object somehow accessible from webrtcbin (1.18)?