Where/how is ATM used ?
ATM is a transmission technique:
A company can implement its own ATM network. Network operators provide fixed ATM connections for subscribers on a permanent contract basis (Permanent Virtual Circuits = PVC)
A network operator can use ATM for internal traffic (so long as QoS conditions of higher layer services are fulfilled). Example: UMTS RAN
In both cases no signalling is required, traffic management is optional!