RBS 2206 comes by default (4+4+4). That is maximum number TRU a 2206 can handle. Unlike 2202, RBS2206 has 6 dTRUs (d = duplex). So 6 physical dTRUs in the cabinet can hangle 12 TRUs, thus giving us 4+4+4 (assuming sectors A, B and C has 4TRUS each). Ofcourse this configurtaion of 4+4+4 is always reconfigurable, depending on the capacity needs. Likewise, we can reconfigure 4+4+4 cabinet to 2+2+2, by phsically removing half of the dTRUs. Ericsson has some preconfigured cabinets such as (2+2+2) or (2+2+0). Its nothing but the removing of the dTRUs. In the real network its more complex than that, we can reconfigure as well as use more than one RBS2206 to get configurations such as (8+8+8) or (6+6+6).
I hope this helps. If you have any other question please dont hesitate to enquire.