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 !