From the RTG website:
RTG is a flexible, scalable, high-performance SNMP statistics monitoring system. It is designed for enterprises and service providers who need to collect time-series SNMP data from a large number of targets quickly. All collected data is inserted into a relational database that provides a common interface for applications to generate complex queries and reports. RTG includes utilities that generate configuration and target files, traffic reports, 95th percentile reports and graphical data plots. These utilities may be used to produce a web-based interface to the data.

I did some contract work for Foreshore linking their Customer Information System (that I developed previously) with their RTG installation, allowing customers to view their own usage online in graph and report form. Customers are restricted to only being able to view their own interface and not those of other customers. RTG doesn't do this by default, it's aimed more at the service provider level than at the service provider's customers.