Using less ATS for a tall building

Hi,

My project is 3 residential blocks. One block has 11 floors, the other two have 45 floors. These blocks have a common basement. There is a riser in each block, it is not in the firefighting shaft. We wish to only use 1 generator for the life safety supplies (LSS). At the moment I’m only considering the LSS for the lighting in the fire fighting shaft (stairs and lift lobbies).  If I allow 1 distribution board per every 3 floors, that’s a lot of ATS’ (automatic transfer switch) needed for each distribution board. Also a LSS is needed for the firefighting lifts (in each block). What would be the best configuration so i can use less ATS’? Bear in mind that the standards state the positions of the ATS’