A few words about the physical layer abstraction that happens in the so-called link performance model in our system level simulator:
1) First, from the subcarrier post-equalization SINR, an effective SINR is evaluated based on the MIESM (Mutual Information Effective SINR Mapping). While theoretically possible, it is in practice unfeasibly complex to obtain a mapping table of all possible combinations of the subcarrier SINR values to a BLER value for each MCS (Modualtion and Coding Scheme).
2) Second, The effective SINR is then mapped by means of an AWGN BLER curve of the corresponding MCS to a BLER value. The AWGN BLER curves are obtained form link level simulations. This would represent the solid line in the example you showed above. To plot this you can use the script LTE_init_load_BLER_curves.m, where the AWGN BLER curves are loaded.
For each user, the effective SINR value is saved in the results file at simulation_traces.UE_traces as TB_SINR_dB, and the BLER value in the parameter BLER. If you want to plot it for specific MCSs, then you have to filter the results for the users that reported a specific TB_CQI.