Within the IETF 90 MMUSIC WG session, Christer Holmberg discussed the future of the "receiver-id" within the BUNDLE draft:
http://www.ietf.org/proceedings/90/slides/slides-90-mmusic-0.pdf

The recommendation (which appeared to have consensus) was to "Use existing SDP mid attribute value as receiver-id" within SDP, as well as to enable the mid to be sent within an RTP extension.

My understanding (please correct me if this is wrong) is that within the context of "Unified Plan" the mid can function as a "trackID", enabling SVC layers (regardless of whether SST-SS or SST-MS is being used) to be steered to an RTCRtpReceiver object. As a result, mid essentially takes the place of the "receiverId".

If that is true, then it would appear to me that references to "receiverId" should be replaced by "mid" in the following places in the document:

Section 8.4
Section 9.1
Section 9.5

Also, the reference in Section A.2 to [APPID] should be replaced by a reference in Section A.1 to an appropriate mid RTP extension draft.