You can place it anywhere in fact as long as you have power
it is used in the US by several police stations and explains in some states that researchers have found rogue telephone towers that asked you to connect to them as if they were the real cell towers.
so next time why would they have to hack Belgacom to trace some cellphones ? Why bother ?
The Belgian privacycommission has been informed by Belsec that several of these installations are in Belgium according to international reports and that is illegal according to Belgian law if they haven't been certified for that.