Sorry, I donot understand clearly what do u mean.
The MSRN is used to setup a connection in the MTC call to a visited MSC, where the MS is currently registered. The originating switch (may be PSTN switch, MSC or GMSC…) used MSISDN of the called party (B nbr) to determine the HLR addr of the MS, and the HLR will setup a signalling conection to the VLR where MS is currently roaming. This MSC/VLR will temporary assign a MSRN for a MS, and return this MSRN to the HLR. The HLR will forward this nbr to the originating switch, and this switch uses this nbr to setup a connection directly to the visited MSC of an MS, as an ordinary call.
If this is not an answer for yr question, plz let me know.