ME and VLR/SGSN are 3G, ICC and BSS are 2G. This applies when e.g. a 2G subscriber with 3G ME roams in a 3G network with 2G BSS.
The situation is like in scenario K, except that with a 2G BSS there is no need to derive CK, IK from Kc in the VLR/SGSN and in the ME. Both, the 3G VLR/SGSN and a 2G/3G dual mode ME can work with 2G AKA.