Multicast

let me give a shot to this question

As Jacobadam has mentioned, ISP do provide IPTV services which can be considered a form of multicasting. But ISP own network cannot be considered as a internet . ISPs network would rather be a service providers private network , but if a host in one corner of world is streaming video from a server in the other end of world and consider there are multiple hosts trying to down load the same file, then multicasting happens over internet.
As far as LAN is considered , I can give a shot that in case VLANs are configured then segregation of users can happen to do a multicast.