LTE: What does eNodeB send "RRC establishment cause " in Initial UE message to MME ?

Question

Need clarity on following items:
1. What is the use of "UE selected plmn" information for an eNodeB ?
2. Is the ECGI/TAI constructed based on the primary plmn (PLMN broadcasted in 0th index in SIB1 ) or based on the UE selected PLMN ?

Answer 1

ENB sends RRC Establishment Cause=mo-Signalling to MME in case, signalling was generated by a UE.

Comments

NAS layer common procedure in this situation rrc connection establishment sends cause with mobile originated signallimg

Answer 2

MME considers "establishment cause" also while taking decision on attach request.
If MME is not configured to support emergency call then it rejects the attach request comes from UE with the rrc establishment cause "emergency".
Not all the users belong to same access class. A MME can accept attach request from user belongs to a specific class while at the same it can reject the attach request from UE belongs to a different access class.
In essence, MME may take different actions based on the different rrc-establishment cause.
I hope this detail will help you !