... however MATS pt 1 Sect 1 Ch4 says
15.1.1 Formations are to be considered as a single unit for separation/deconfliction purposes
provided that the formation remains within the parameters shown etc etc.
Notwithstanding rule 14, I would suggest that although it doesn't specifically mention landing clearances (or take-off either) that the controller would be clearing a single unit to land. Certainly formation t/o are common - witness airshows.
I think they are pretty explicit there, formations are to be considered a single unit for sep/deconfliction, if they intended that rule to cover landings, they would state it.
As far as my book of rules and tools is concerned I cant find anything allowing me to clear a formation to land.
If someone does come up with something, let me know, it would make my job simpler.
I'd take airshow formation stuff as a special case, the individuals involved being subject to specific checkouts and permisions (i think?)