This depends on the provider. Their choice on this.
HOWEVER with Internet addresses at a premium even a leased line may not be a fixed address and even if it was, many companies I know put a router on that and DHCP the clients.
As i know ,the ISP used to provide dynamic ip address through DHCP. If i am using leased line for internet connection, in this case which type of ip address will be assigned by ISP. Is it static or dynamic ?